When this type of work was introduced into the laboratories of this country, almost any available material was used. This material was studied in great detail, important and trivial things being kept at a dead level. The purpose was to train in observation rather than to develop any picture of the plant kingdom. This detailed study meant the handling of a few types. The pedagogical slogan of those days was a few types thoroughly studied. The few types selected were naturally those most available, and by some irony of fate these most available things turned out to be the most unrepresentative types possible. You are familiar with the old list: Spirogyra, standing for green algæ; Marchantia, for liverworts; a leptosporangiate fern, for pteridophytes, and so on. Now all this has been changed. The purpose is to give some conception of the evolution of the plant kingdom, not in detail or in any rigid way, but in general perspective. The threads on which the facts are strung are such as these: the transition from a one-celled to a many-celled body, the evolution of reproductive methods, the origin and differentiation of sex, the acquisition of the land habit, the origin and development of the alternation of generations, the origin of the leafy sporophyte, the evolution of the vascular system, the evolution of the seed, the origin and evolution of the flower. How can "a few types thoroughly studied" illustrate such things or give any such perspective?

This means means much illustrative material, carefully selected, and each form used to illustrate some definite and important fact. It is not many types hastily studied, but many types studied carefully for the few points that are really important. The difference between the older view and the recent one, both in teaching and in research, is the difference between an indiscriminate mass of unrelated Details obtained from a few representative forms, and a selected mass of related details obtained from a large number of representative forms.

These somewhat miscellaneous statements may serve

to illustrate the point of view that has been developed, which after all is the significant thing in our progress. It would be tedious and unprofitable to enumerate the long list of important new facts that have been discovered. Besides, these new facts are most of them so technical that any brief reference to them would be intelligible only to those who do not need the information. In closing, I may venture to suggest a future development which seems extremely desirable. The general problems upon which we are now engaged must involve the examination of an enormous amount of material before we can feel any confidence in our conclusions. It ought to be possible to associate investigators or laboratories in a general attack upon any problem conceded to be important enough to justify such a united effort. Whenever this has been done in a laboratory possessing several investigators, the result has been striking. We must begin to combine our detached efforts, the guerilla method of attack, and support individual effort by association. The scheme is only a thought, and the details may make it impossible, but I believe that we have reached a point where something of this kind is demanded for definite and substantial progress.

II. THE PROGRESS OF PLANT ANATOMY DURING THE PAST

DECADE

PROFESSOR EDWARD C. JEFFREY

HARVARD UNIVERSITY

THE fascinating problem of the alternation of generations in the higher plants is responsible for the fact that the attention of morphologists, since Hofmeister, has been turned largely to the spore-producing organs and the gametophytes. This tendency can be counted as entirely fortunate, for the closer affinity of the gametophyte with the presumably ancestral forms and the progressive re

duced and simplified structure, which it presents in the vascular series, has made it particularly suitable for the initial stages of modern morphological development. With the discovery of zoidogamous fertilization in Cycas, Ginkgo and the lower fossil gymnosperms, the revelation of the remarkable mode of fertilization in the Araucarineæ, simulated at least in the Podocarpineæ, the uncovering of the phenomenon of breech fertilization in the lower Amentiferæ and the elucidation of other striking phenomena connected with the male gametophyte, we have come to realize that it is the male sexual generation and the sporogenous apparatus, producing it, which carry the highest phylogenetic interest. The origin of the seed from the megasporangium, although beyond question on general morphological grounds, still largely lacks illuminating facts to lighten the darkness of its past.

The more complicated sporophytic generation of the higher plants, except as to its special sporogenous structures, has much more recently been attacked by evolutionary morphologists. Its very complexity, however, and the possibility of following its structures into the remotest past, make it of the greater importance from the standpoint of the theory of descent. The evidence derived from its study serves, moreover, to control, amplify and enrich the conclusions reached from the standpoint of the morphology of the gametophyte alone. We have, accordingly, begun to realize that the anatomical examination of the sporogenic organs of vascular plants is quite as important as the cytological study of the process of sporogeny itself, and that the fern-like mode of fertilization obtaining in the lower gymnosperms, living and extinct, has its not less important or significant equivalent in the presence of cryptogamic or centripetal primary wood. In fact, with the realization of the importance of the sporophytic generation in the higher plants, we are now for the first time in a position to begin our phylogenetic bookkeeping by double entry, with greatly added security as to the final accuracy of the balance we may strike.

Perhaps nowhere is the advantage of morphological bookkeeping by double entry more clearly illustrated than in the case of the conifers. Forming with the other living gymnospermous species a restricted but illustrious "four hundred," they have quite held their own in botanical interest, in spite of the overwhelming numbers and importance of the modern mob of angiosperms. The older and entirely superficial morphology, led to the conclusion that simple forms and structures are more primitive. On this basis the conclusion was reached that those simple and coneless conifers, the Taxineæ or yews, are the oldest and that the pines or Abietineæ, with their very complicated cone-structures, are most modern. It has, moreover, been inferred that the coniferous tribes represent a series of progression beginning with the yews and ending with the pines. The microscopic study of the gametophytes began the disintegration of this system. The discovery of zoidogamous fertilization in Ginkgo, which in Engler and Prantl's Natürliche Pflanzenfamilien, you will find included with the yews, made it at once apparent that this remarkable genus, sole survivor of an abundant stock, once flourishing through the entire northern hemisphere, could not be included under the Taxineæ, or link the latter with the still more ancient Cordaitales, confined to the Paleozoic. Thus deprived of the reputation of an illustrious ancestry, the yews have since been disrespectfully kicked up the phylogenetic stairs by the younger generation of gametic morphologists. A corresponding but reversed process has in the meantime taken place at the other end of the coniferous series. It has been shown by the gametophytic morphologists, that the sexual generations of the pine tribe are more complicated, and for that reason more primitive in the reduced members of the alternation, than any other conifers, characteristically found in the northern hemisphere. From the sporophytic side it has been shown that the cone-structure of Pinus affords an anatomical explanation of the strobilar organization of the other tribes of conifers on the basis

of commonly accepted principles of reduction and adhesion. Further, it has recently been discovered that the leaves of the ancestral pines (Prepinus) had the same cryptogamic type of centripetal wood-bundles, which are found in the Cordaitales, universally regarded as the Paleozoic stock to which the conifers as a whole are most nearly allied. There is further evidence of the antiquity of the Abietineous or pine tribe based on important experimental data and on the origin of coniferous pitting, which need not be entered upon here. If, in accordance with the facts very briefly indicated above, we cast up our phylogenetic balance by double entry for Pinus, we find it on both sides overwhelmingly in favor of the superior antiquity of the Abietineæ, or pines, as compared with the Taxineæ, or yews. It would take much too long to cast even hastily the balances for the remaining tribes of conifers and in the case of those at present mainly or wholly confined to the southern hemisphere the data are as yet not complete. Even though the books are not yet ready to be opened for the final judgment, the results of recent morphology on both the gametic and sporophytic sides make it clear that the conifers, contrary to the conclusions of the old superficial morphology, are a series of reduction and not one of progression and that their most complicated forms are consequently the oldest and those of simplest guise the most modern.

One of the most striking confirmations of the truth of the theory of organic evolution is found in the recapitulationary phenomena of animals. The colt, for example, in the course of its individual development passes through the phases of progressive loss of digits, presented geologically by the equine stock from the Mesozoic to the present. The young mammal in its earlier stages of ontogeny possesses the gill arches and the segmented musculature of the fish. In the principle of recapitulation presented so clearly in the development of animals, our zoological brethren may fairly claim that on their side of the house the truth of evolution is declared by the