ON ROOT HAIRS..

BY TH. JAMIESON, ABERDEEN, SCOTLAND.

DURING the past fifteen years, in the course of carrying out a very large number of experiments to ascertain the relative effects of different forms of manure, and also, which of the mineral chemical elements usually found in plants are essential, no point was more strikingly illustrated than the inability of the plant to grow in the absence of phosphorus, although all the other essentials of growth were fully supplied. In its absence, the turnip plant, for instance, reached the stage of forming only leaflets, while neighboring plants, treated in every respect in precisely the same manner, only that they were supplied with phosphorus in addition, developed large plants, yielding a crop of about 30 tons per acre. laboratory or lecture room experiment could be more effective than the positive and negative results shown by two such plots, side by side, and these evidences have been abundantly repeated annually.

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In following out an inquiry bearing on this remarkable action, a special microscopic examination of root hairs was suggested; special in respect of introducing various conditions of light and shade, even approaching darkness, as well, of course, as adjustments of the focus under various degrees of light. This is specially mentioned in order to indicate that the feature on root hairs about to be explained is such as might easily escape notice in an ordinary examination. An unlooked-for structure was thus detected, as a consequence of attention being so long concentrated on the tip of the hair and of gazing continually on the spot under cautious and slight alterations of both

light and focus. It was seen that there was a well defined aperture. The aperture in the first case of detection was so clearly defined, and moreover seemed so clearly continuous with the inner membrane or tube of the hair cell, that no doubt was felt that there was an aperture. Possibly it would not have been discerned had it not been on an unusual part of the hair, viz.: a little below the point, so that the point formed a kind of cap. As a rule, however, the aperture is at the point.

So necessary is it to examine the root hair under varying conditions of light and focus, and also to travel along the inner lining of the tube with the eye till it reaches the point where the aperture ought to be, and so frequently is the aperture turned away from the point of view, that one familiar with the process can easily understand how any one not so familiar might rise from the examination and feel satisfied that the hair is, in deed, a a closed tube. Only persistence to continue, till the inexperienced observer falls upon a suitably placed hair, is followed by success.

After having observed so satisfactorily the first aperture, much time was spent during three years in examining the hairs of a large number of plants, and although from the state of the plant roots, and the condition and position of the hair, the aperture has frequently not been detected at the first examination, yet by another selection and persistent examination the aperture has been found without exception in the case of every plant examined.

On examination at this stage of the writings of the more eminent botanists on the subject, it was found that in few of these treatises is the detailed form of the hair gone into with sufficient minuteness.

The works of De Bary, Duchartre, Olivier, Gasparina, Van Lieghem, Sachs, Vines have been referred to.

The essential and accepted character given in all these works is: a complete and closed cell, thread-like in form

and broadened at the base, where it is continuous with, and forms part of, the epidermis.

The more recent works by Schwartz, Zacharias and others dealing more particularly with root hairs have been examined, but the idea of an aperture does not seem to have occurred to them, and the negative evidence, of course, is not of any significance.

Referring now to the function of hairs as bearing on an aperture. None of the writers on the minute structure of hairs departs from the idea that the hairs are closed cells, or, as Sachs describes them, exceedingly delicate walled narrow tubes.

By accepting this view a difficulty arises. It has hitherto been found necessary to advance some explanation, for the well-known fact that the insoluble matter, such as phosphates, is assimilable by plants. Sachs says in expla

nation that these insoluble matters are without doubt dissolved in the thin layers of water which surround the particles of soil, basing this inference on the fact that water running off from the drained pipes of tilled soil contains these substances; but he infers further, that "since the nutritive materials clinging to the particles of soil are not soluble, or but slightly so in water, the roots must themselves effect the solution." This seems to be a kind of forced conclusion, i. e., as the insoluble matter does get in, the particles must be dissolved, and, he asserts, without, however, giving grounds for it, that this solution is accomplished by means of the extremely thin membrane of the root hair being permeated with an acid fluid. Now, it is obvious that, it being once accepted that the root hair is a closed tube, and that side by side with this acceptance is placed the well-known fact that plants make use of insoluble matter, it becomes a necessity to assume, and it appears little more than an assumption, that the plants obtain their solids by the action of an acid. The usual statement is, not that the plant roots make use of an acid, but that they must make use of an acid, thus indicating that there was no other way of getting over the difficulty.

Van Tieghem also says that the roots set free an acid liquid which bathe their surface. He, however, undermines that statement by summarizing the functions of the root as a threefold action on the soil:

First On the gases, by absorbing oxygen and disengaging carbonic acid.

Second-On the water and dissolved matter, by absorbing them.

Third-On the solids, by dissolving them.

Now, it is evident that if the root acts so as to disengage carbonic acid, that acid alone is sufficient to account for the reddening of the litmus; and this circumstance takes away the support that such acid reaction might seem to give to the assumption that the plant forms an acid to dissolve the mineral food, unless, indeed, the dissolving acid be simply carbonic acid, in which case it would be uncertain whether the acid is there to dissolve insoluble matter, or is there as a simple product of decomposition. composition. Vines asserts, however, that the reddening is permanent, and therefore is not due to carbonic acid.

Considering the slight evidence thus provided by Sachs and Van Tieghem, and that no observers seem to have found any special acid in the root, but simply acidity that may be accounted for by decomposition of the plant, or of organic matter in the soil, the dissolving action of the root hair seems to be little more than an assumption rendered necessary as an explanation of the well-known fact that insoluble matter is assimilated by the plant.

A difficulty in accepting the passage of solid particles by an aperture may seem to be presented by the consideration that, if solid particles enter the hair tip by an

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with the deeper tissue, or possibly with the vascular tisThus in examining the root hair of a carrot, the faint bluish-grey appearance of the central tube was seen to be continuous with the deeper tissue, though whether entering into a vessel, or simply passing between the cells, could not be distinguished. This relation of the hair with the deeper tissue is supported by the origin of hairs as described by Schwartz and Duchartre. But there is

seen that they vary not a little, both in shape and position, being usually a minute circular hole at the extreme, and more or less tapered, end of the inner tube, with, of course, a correspondingly larger rim in the outer tube; but sometimes the opening is transverse, sometimes not quite at the tip, or, rather, the tip seems half curved, making the aperture appear slightly at one side, and the tip to appear like a lip or knob.

LABORATORY WORK BY THE STUDENT OF CHEMISTRY SHOULD BE SUBORDINATE AND AUXILIARY TO THE DEVELOPMENT OF FACTS, PRINCIPLES AND THEORIES BY THE TEACHER.'

BY R. W. JONES, UNIVERSITY OF MISSISSIPPI.

THOSE of us who are engaged in teaching chemistry recognize the fact that it is a difficult subject to teach scientifically; it is ofttimes hard to make its lessons clear to the mind of the student; difficult to employ it with its due power as a means of intellectual discipline and an element of general, liberal education; and yet it has a place, an accorded place, in every properly arranged scheme of education: no such scheme is complete without it, and no one can be said to be liberally educated who has not learned the elements of this science; for without the knowledge of these elements, at least, it is impossible to read understandingly the literature of our day and to appreciate a thousand things of common occurrence in respect to health, well-being and progress. The practical utility of chemistry is unquestioned; but some question its disciplinary value as an element of general education. In my opinion, the skillful teacher makes its value in this regard equal to the languages and mathematics, and gives to the mind exercise and truth which in character are peculiar and in quality most valuable.

The great value of the study of general chemistry turns solely on the adoption of good, sound methods of instruction.

The nature of the subject, the inquiry into strange forces, into marvellous activities and changes, give to it, in the eyes of beginners, the appearance of the mysterious, making it seem, as it did to the Egyptians, a "Black or Secret Art." The puzzling vastness of the number of facts, the important and interesting relations between them, the comprehensive laws, the profound theories, tax the powers of the capable and patient student.

The teachers and the writers of text-books often find it difficult to decide what to use and what to omit of this profusion of material. The subjects can be so selected, the matter so arranged with due regard to the time at our disposal and such methods of instruction employed that no other subject could be profitably substituted for the study of chemistry.

The methods of teaching general chemistry have. varied greatly at different times and now vary more or less in different schools. Of course, each teacher carries his personality into his class room: this is right and inevitable; there are differences of method which are broader, proceeding from difference of standpoint and difference of view both of the object to be accomplished and the way of reaching it.

We cannot emphasize too strongly the general disciplinary value of the study of chemistry and its essentiality to culture; and it devolves upon us to maintain the correctness of our estimate by the intellectual and industrial results of our teaching. The first object is to use chemistry in a scheme of education to make intellectual men, and the second is to prepare skilled chemists.

After noting these differences of method, I am sure we may all agree that the feature which specially characterizes the teaching of chemistry at present and which distinguishes it from the method of past years is experimentation by the student.

And yet in many high schools and colleges, even in this day, the effort is made to teach chemistry without experiments either by the instructor or by the pupil. Many 1Read before the International Congress of Chemists, Chicago.

of these schools and colleges have no apparatus. Such teaching of chemistry and of science generally is illusory. Chemistry is justly and highly valued in its general study as an element of disciplinary power and as a foundation for special attainments; but its most earnest and intelligent advocates in a course for a well-rounded education would admit that it would be far better to omit it altogether than to teach it in that irrational manner without experiments, and to devote the time thus saved to the study of some subject which can be scientifically taught without apparatus.

As teachers, we must insist that an experimental science, such as chemistry is, cannot be taught without experiments.

In my judgment, the best method of teaching general chemistry, in the earlier part of the course, the best way of laying a substantial basis of knowledge that is reliable and definite, on which the student can subsequently build most surely and rapidly, is for the professor to give in didactic style oral lectures, adapted to the comprehension of his class, setting forth in order the most important portions of the great body of established facts, connecting them by threads of scientific relation, that bring them into a simple unity, illustrating them by experiments, on the lecture table, which cover all essential points and help the minds of students to apprehend them as real.

A really good text-book is very valuable, and the instructor ought either to follow the order of subjects in the text-book or be careful in assigning the readings so that the lectures and text-book will each day cover the same ground substantially. Otherwise confusion of thought will arise in the student's mind.

To indicate something of the scope of instruction I would say that there should be a clear presentation of the nature of chemical science, its relation to other sciences, and the ways of doing the work: there should be a discussion of the elements and their most important, best known compounds: as the teacher's knowledge

covers his whole course he is able to call attention to that which is essential and that which may be at the time incidental, to note the connection between facts, the relation between substances, and thus to systematize and organize knowledge and build up the science in the minds of students: this prepares the way for the proper presentation and discussion of laws and theories, for calling into vigorous exercise the faculties of comparison and judgment. He can exhibit the method of properly guarded generalizations and formulations of his teachings; his duty and plan are to guard the student against the presumptuous thought that one man can make experiments to cover all the facts and phenomena and demonstrate all the laws of chemistry, and to impress on the mind respect for the work that has been patiently done by others and thus give a just regard for authority, through which so much of our knowledge comes in every department of inquiry: the pupil learns that for a satisfactory demonstration of chemical truths he needs a large complement of facts and processes.

At each meeting the class should be questioned upon the matter of previous lectures and readings; skillful repetition is needed to make distinct and abiding impress of the truths, to wear off the strangeness of the subjects and to get a lodgement of the facts and princiciples.

The careful keeping of notes, subject to periodical inspection of the teacher, the writing of chemical reactions and the solution of problems constitute an important part of that instruction which is necessary to exactness in method and clearness of understanding. It goes without saying that the student must be taught to

make experiments. But in order to carry out this plan, the experiments to be made by him should be connected with the course of instruction and should be definitely related to the experiments given on the instructor's table. Indeed, the relation should be so close that a knowledge given by the instructor's experiments would be in large measure a guide to the performance of the student's experiments and that without it the successful performance of the practical work by the student would be beyond his power. This insures the closest attention and care on the part of the student to get the professor's instructions; it trains the mind to correct observation, concentration of energies and carefulness in drawing conclusions.

In the beginning of a course in general chemistry and for two or three months, one hour of laboratory work by the student to four hours of such instruction by the professor, as I have outlined, will be a good division of time. As the student's knowledge of the subject increases and his manual dexterity in handling apparatus improves, his working hours should increase. This mode of instruction proceeds on the rational assumption that the pupil needs to be instructed; it will furnish him the largest amount of reliable, systematic, classified knowledge that is attainable in a given time and give him the best foundation for extended scientific study.

Other special advantages of this mode of study will appear by comparison.

Many excellent chemists make laboratory experiments by the student the starting point and the centre of all instruction. Their idea seems to be to make the student do his own work, draw his own conclusions and thus instruct himself: the instructor, according to this method, gives him the fewest practicable hints and directions. In furtherance of this plan of instruction many "laboratory manuals" have been written which contain a great profusion of experiments: in many cases these are poorly arranged. In the preface to one of these "manuals," now open before me, I find these words: "The teacher should be but the guide that points out the right path, calling attention to the bypaths of error." This plainly implies that if only the direction be pointed out, the student can make the trip. This plan puts the student forward to work for unknown truth; it holds out to him the idea that in some sort he is an investigator, when in reality at first his work should be to learn what others have brought to light and how they have done it.

The objections to making the laboratory work of the student in the beginning the leading and independent method of learning chemistry are numerous and strong: 1. It involves an unnecessary consumption of time. 2. It assumes that the student can do properly what, in the very nature of the case, is well-nigh impossible. A certain amount of knowledge is necessary to the acquisition of other knowledge under the best conditions: there is hardly any fact more palpably true than this.

A student of algebra could hardly be expected to solve problems of any degree until he had the preliminary operations and rules that had been established by the patient work of strong, industrious minds. A traveller, ignorant of the topography and history of Rome, her archæology, her classic and Christian art, would not be profited by a visit to the famous city: he would stand unmoved before the ruins, the historic arches and temples and the treasures of her splendid galleries. A man sees what he has eyes to see. principle applies in the study of chemistry. An untaught youth knows not what to expect, what to look for in an experiment; he sees things and knows not what is essential and important and what incidental and

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accessory. Many things he fails to see because he knows not what to look for and how to look. This brings him into a hesitating, doubting state of mind which is very unfavorable to definite, strong impressions. He does not know the significance of those actions which he observes, and he is unable to give them scientific interpretation and impression.

Chemistry is a great science, difficult to master: it has risen upon stepping stones of errors and obstacles by the continued efforts of great men. For centuries minds of able and laborious investigators reached out after the truth and battled against error. The advance from the unknown to the known has been very slow.

Glauber's "Sal Mirabile," Shahl's "Phlogiston" and various other propositions and hypotheses, strenuously advocated and rejected, tell us of the intensity of the struggle and how the mists of uncertainty hung over their work. But when Lavoisier availed himself of the labors of others, patiently compared facts with facts and generalized scientifically, he saw a new light, and the birth of modern chemistry was announced; chaos gave place to order; principles became harmonious.

In view of all this, is it not erroneous to require a student in the very outset to make and interpret experiments as the means of getting knowledge and to proceed with the most meagre knowledge to classify phenomena? Students at first should be put in possession of that knowledge which is their just inheritance from the history of the past and should have the opportunity of learning the methods of experimentation adopted by the builders of the science, and from this study of facts and principles and modes of manipulation to acquire the power of orderly thinking and get the key to higher and greater treasures.

When one wishes to enter upon research he carefully inquires what has been done already; he gets the bibliography, and learns the methods of investigation in that line that have been most fruitful of results: not uutil he has come to this point is he ready to enter upon the work which he proposes.

The object of work in the laboratory by the student in the beginning is to learn to use apparatus: his instruction must come mainly from the skillful teacher: the teacher is not merely "a guide" but a positive power in instruction, an intellectual quickener. The work of a student left to himself in the laboratory profits but little.

ORIGIN OF THE HYDROCARBONS.

BY MARCUS E. JONES, SALT LAKE CITY, UTAH. A RECENT review of the paper of Dr. Engler on this subject in Science is an interesting one, as it is in the line with my own observations on that subject in Utah. The time-worn theory of the origin of our Utah hydrocarbons from coal has been repeated by several persons in Science during the past year, but unfortunately there is hardly a particle of evidence of such origin. I do not know of a single deposit near our coal beds in Utah, with perhaps the exception of one bed of impure asphalt, which seems to be close to the Dakota group, but may have come down from al ove, as it is not certainly interstratified with the Cretaceous beds. With this exception I do not know of any deposits of our hydrocarbons that are earlier than the Miocene Tertiary. There are some places where it is not possible to certainly tell whether some sandstones are Eocene or Miocene where asphalt has collected from adjacent beds of shale or clay. In using the word "near" it is used in a geological sense, i. e., stratigraphically near. There are some hydrocarbon beds which are within perhaps one-half a