40 



SCIENCE. 



[N. S. Vol. XXI L. Xo. 550. 



sporophylls as that sporophylls are transformed 

 leaves. * * * To call a stamen a modified leaf is 

 no more sound morphology than to call a sporan- 

 gium derived from a single superficial cell a 

 modified trichome. The cases of ' reversion ' cited 

 are easily regarded as cases of replacement. Lat- 

 eral members frequently replace one another, but 

 this does not mean that one is a transformation of 

 the other.* 



We see that in this verdict the emphasis 

 is laid on the historical development, but 

 at the same time this is pointed out to be 

 unknown to us. With this latter conclu- 

 sion I am in complete harmony, but the 

 accentuation of the historical-phylogenetic 

 factor has, on the other hand, led to a con- 

 ception of the ontogenetic problem, in 

 which I can perceive no advance upon the 

 old morphology; there is rather avoidance 

 of the problem than an attempt to solve it. 

 This, however, is connected with the purely 

 formal conception, as the phylogenetic 

 morphology employs it. Let us examine 

 the matter in question. For a long time 

 we have known that often in the room of 

 the stamens — to confine ourselves to these 

 — flower leaves or foliage leaves or occa- 

 sionally even carpels arise. The idealistic 

 morphology says that this proves that the 

 stamens are 'leaves,' for these can be 

 modified the one into the other. Coulter 

 and Chamberlain, however, deny that a 

 stamen fundament may be transformed 

 into a flower leaf; they find only a 're- 

 placement' of one 'lateral member' by an- 

 other. It should be remarked that ' leaves ' 

 exist in nature as little as 'lateral mem- 

 bers.' Both notions are mere mental ab- 

 stractions, not the expression of the facts 

 of observation. We speak of the replace- 

 ment of one organ by another if these have 

 nothing more in common than the place of 

 origin. Thus we see that in the foliose 

 liverworts a branch often arises in the posi- 

 tion of a leaf-lobe. No one has observed 

 any intermediate form between these; the 



* Coulter and Chamberlain, ' Morphology of the 

 Angiosperms,' p. 22. 



lateral shoot in reality takes only the posi- 

 tion of a leaf-lobe. The relation between 

 the stamens and the organs which 'replace' 

 them is, however, quite different. We 

 speak of a transformation of an organ A 

 into an organ B when B not only stands in 

 the position of A, but also corresponds 

 with A in the earlier stages of its develop- 

 ment, and later strikes out on its own line 

 of development. If this is the case, we 

 should expect to find between A and B in- 

 termediate forms which are different ac- 

 cording to the developmental stage at which 

 A is caused to develop further as B. To 

 use an analogy: Replacement and trans- 

 formation behave as two fluids which are, 

 and two fluids which are not miscible; in 

 the first case the inner structure is differ- 

 ent, and in the second there is a corre- 

 spondence. The comparison is a limping 

 one, but still gives us a fair illustration. 



As a matter of fact, we do find every 

 intermediate step between stamens and 

 flower leaves, and we can not doubt that 

 these have come into existence because a 

 stamen, or, in other words, a stamen funda- 

 ment, has at different stages of its devel- 

 opment received a stimulus which has 

 caused it to develop into a flower leaf. 

 We find correspondingly, that the earlier 

 developmental stages of a stamen and a 

 flower leaf are parallel throughout, while 

 in the above cited example of the branch 

 and a leaf-lobe of a Jungermanniaceous 

 liverwort the developmental history are 

 throughout different, as is shown by the 

 arrangement of cells. In the case of sta- 

 mens, therefore, there occurs not a replace- 

 ment, but a transformation. And, indeed, 

 a limited one. Not any 'lateral members' 

 you please may arise instead of stamens, 

 but only and always those which we sub- 

 sume under the concept leaf, because they 

 evidently have peculiarities in common. 

 Besides, there are also normal flowers which 

 exhibit all intergradations between flower 



