< Page:Popular Science Monthly Volume 7.djvu
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THE POPULAR SCIENCE MONTHLY.

to introduce the student to the present state of knowledge in botanical science. He not only explains the phenomena of plant-life already accurately known, but also indicates those theories and problems in which botanical research is at present engaged. References are given throughout the volume, which direct the student to those writings that contain fuller discussions of the points in question, that he may be enabled to form for himself an enlightened judgment. The illustrations are mostly original, and many of them the result of laborious investigation.

The work consists of three divisions: General Morphology, Special Morphology, and Physiology. Under General Morphology, there are three chapters treating: 1. Of the morphology of the cell; 2. Morphology of the tissues; and 3. Morphology of the external conformation of plants. Special morphology deals with the groups of plants as at present arranged in classes. Physiology is treated in seven chapters: 1. On the molecular forces in the plant; 2. Chemical processes in the plant; 3. General conditions of plant-life; 4. Mechanical laws of growth; 5. Periodic movements of the mature parts of plants, and movements dependent on irritation; 6. The phenomenon of sexual reproduction; 7. The origin of species.

The general reader, who is interested in modern scientific discussion, will find this an entertaining volume, because of its vital relation to questions uppermost in modern thought. For instance, the world-wide interest in "protoplasm" aroused by Prof. Huxley's address at Edinburgh, finds ample satisfaction in the explanations of cell-structure and cell-function. As bearing upon this subject we quote the following, which will be new to many readers:

"Under this head" (Myxomycetes) "is included a numerous group of organisms which, in many respects, differ widely from all other vegetable structures, but, in the mode of formation of their spores, stand nearest to fungi, on which account we may treat them as a supplement to that class. The Myxomycetes are remarkable in no ordinary degree from the fact that, during the period of their vegetation and assimilation of food, they do not form cells or tissues. The protoplasm, which in all other plants is also the general motive power of the phenomena of life, remains in them during the whole of this period perfectly free, collects into considerable masses, and assumes various shapes from the internal force residing in it without becoming divided into small portions, which surround themselves with cell-walls (or become cells). It is only when the protoplasm passes into a state of rest in consequence of being surrounded by unfavorable conditions, or when it concludes its period of vegetation by the formation of the reproductive organs—its internal and external movements ceasing at the same time—that it breaks up into small portions which surround themselves with cell-walls, and which even then never form a tissue in the proper sense of the term."

The book is penetrated throughout with modern views in biology, and also illustrates the truth of the remark that, while other nations are disputing about the doctrines of Darwin, the Germans accept them, and are working on the new basis afforded by them. In the chapter on the "Origin of Species," full of the fruitage of this new line of study, we find the following:

"The scientific basis for the theory of descent rests in the fact that it alone is able to explain in a simple manner all the mutual relationships of plants to one another, to the animal kingdom, and to the facts of geology and paleontology, their distribution at different times over the surface of the earth, etc.; since it requires no other hypothesis than descent with variation, and the continued struggle for existence which permits those forms only to persist that are endowed with sufficiently useful properties, the others perishing sooner or later. But both these hypotheses are supported by an infinite number of facts. The theory of descent involves only one hypothesis that is not directly demonstrated by facts, namely, that the amount of variation may increase to any given extent in a sufficiently long time. But, since the theory which involves this hypothesis is sufficient to explain the facts of morphology and adaptation, and since these are explained by no other scientific theory, we are justified in making this assumption."

Sixth Annual Report of the State Board OF Health of Massachusetts. 379 pages. January, 1875.

This report opens with a feeling tribute of respect, from the pen of Dr. Henry I. Bowditch, Chairman of the Massachusetts State Board of Health, to the memory of

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