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SCIENCE. 



[N. S. Vol. XX. No. 515. 



structure to the limits of technique. It is 

 becoming more and more clear that every 

 morphologist must also be a cytologist ; and 

 certainly every cytologist should be a mor- 

 phologist; and there is no more reason for 

 differentiation on this basis than on the 

 basis of objectives used. 



While fully recognizing the magnificent 

 development of morphological knowledge 

 that has resulted from this point of view, 

 it is interesting to note running all through 

 it much of the rigidity of the older mor- 

 phology, leavened to a certain extent by 

 the demands of evolution. Certain definite 

 morphological conceptions were established, 

 and organs were as rigidly outlined and 

 defined as under the old regime. For ex- 

 ample, there were no more definite mor- 

 phological conceptions than sporangium, 

 antheridium and archegonium. Uncon- 

 sciously, perhaps, a type of each was se- 

 lected, this time from their display in the 

 lower, plant groups ; and this type was read 

 into the structure of higher groups. The 

 distinctly outlined antheridia and arche- 

 gonia of bryophytes were compelled to re- 

 main just as distinct of definition when 

 they become confused among surrounding 

 tissues in the pteridophytes ; and the beau- 

 tifully distinct sporangium of the leptospo- 

 rangiates compelled the idea of an im- 

 bedded sporangium among the eusporan- 

 giates.- In other words, the concept included 

 non-essential with essential structures, a 

 distinct wall about a sporangium being just 

 as much a part of the definition as the 

 sporogenous tissue, and its presence com- 

 pelled even in the absence of any occasion 

 for it. It can hardly be doubted that this 

 was a heritage of habit from the older mor- 

 phology, for it is in a sense a continuation 

 of the conception of types. The recent 

 morphologist who traces a sporangium wall 

 into an anther is the same in spirit as the 

 older morphologist who saw in the stamen 

 a transformed leaf. 



Associated with this rigidity of concep- 

 tion as to structure was the idea of predes- 

 tination, and search was made for the cell 

 or cell-group that was foreordained to pro- 

 duce a given structure. There was no idea 

 that the fate of these cells might be changed 

 or that other cells might share it. The re- 

 peated attempts to discover an exact defini- 

 tion of the term archesporium will serve 

 as an illustration ; and the repeated failures 

 should have warned sooner than they did. 

 Indifference of primordia was not thought 

 of, and each living cell was conceived of as 

 having only a single possibility. 



The idea of unvarying sequence and pre- 

 destination not only entered into the con- 

 ception of developing organs, but also di- 

 rected an immense amount of work in con- 

 nection with the early embryonic stages of 

 both gametophyte and sporophyte. So far 

 as my own experience is concerned, it was 

 in this connection that the conception of 

 rigidity broke down. The multiplication 

 of observations caused definite sequence 

 and predestination to vanish in a maze of 

 variations. This type of morphology was 

 necessarily its own corrective, for rigidity 

 could not stand before the accumulation of 

 facts. In a sense, rigidity of conception is 

 easier to grasp and certainly- simpler to 

 present than flexibility of conception, for 

 the human mind seems to demand its 

 knoAvledge in labeled pigeon-holes. This 

 same spirit permeated the attitude of the 

 morphologist of this period towards his 

 ultimate purpose, for phylogeny to him was 

 rather a simple conception. Similarity of 

 structure meant community of descent. 

 Such a condition as heterospory, such a 

 structure as the seed, or such an organiza- 

 tion as the sporophyte was attained once 

 for all, and the successful plant or group 

 became the fortunate ancestor of all hetero- 

 sporous plants, or spermatophytes, or spo- 

 rophytes. This was phylogeny made easy. 

 Multiplied observations showed that simi- 



