January 16, 1903.] 



SCIENCE. 



101 



still found almost all intermediate condi- 

 tions, culminating in the large and com- 

 plex sporangia of the true mosses, and the 

 someAvhat similar but much simpler one of 

 Anthoceros. 



In following such a series it is clear that 

 spore-production, the sole function of the 

 primitive sporophyte, becomes largely sub- 

 ordinated to the purely vegetative exist- 

 ence of the sporophyte. Thus in such a 

 moss as Polytrichum, the sporogenous tis- 

 siie does not appear until a late period in 

 the development of the sporophyte, and 

 comprises but a very small fraction of its 

 bulk. An elaborate system of assimilative 

 tissue, with lacunar green tissue and 

 stomata like those of the vascular plants, 

 is developed, and the loss of water due to 

 transpiration is made good by a strand of 

 conducting tissue, which represents a sim- 

 ple tj-pe of vascular bundle. 



While the elaborate sporophyte of the 

 mosses offers certain suggestions of the 

 structures of the vascular plants, it is much 

 too highly specialized in other directions to 

 make it in the least probable that it has 

 given rise to any higher forms. The 

 equally dependent but much simpler sporo- 

 phyte of the peculiar group of the Antho- 

 cerotales is probably very much more like 

 the forms from which this independent 

 sporophyte of the ferns arose than is the 

 more highly developed sporogonium of the 

 true mosses. 



The subject of the gradual elaboration 

 of the sporophyte cannot be dismissed with- 

 out reference to the very important work 

 of Professor Bower, whose clear exposition 

 of the progressive sterilization of the tis- 

 sues of the originally exclusively sporo- 

 genous sporophyte is one of the most im- 

 portant contributions to the subject. 



When we review the extraordinarily 

 large number of resemblances between both 

 gametophyte and sporophyte in the ferns 



and liverworts, the weight of evidence, to 

 my mind, is overwhelmingly in favor of 

 assuming a real genetic connection between 

 the tAvo groups. To say 'that no structures 

 among plants seem to have left so little 

 trace of its origin as do the leafy sporo- 

 phytes of Pteridophytes and Spermato- 

 phytes,' is certainly to ignore all the prin- 

 ciples of comparative morphology. When 

 we reflect that the reproductive organs 

 and mode of fertilization are the same in 

 all archegoniates ; that the early divisions 

 and growth of the embryo are identical; 

 that in the more specialized bryophyte the 

 sporophyte develops assimilative and con- 

 ductive tissues strictly comparable to those 

 of the Pteridophytes ; and finally, that the 

 spore formation is identical to the minutest 

 details ; surely such a statement is very far 

 indeed from stating the truth. 



The fallacy of the arguments based upon 

 apogamy has been ably refuted by Pro- 

 fessor Bower. He has called attention to 

 the fact that nearly all cases of apogamy 

 are abnormal, and occur in forms where 

 the sporophyte normally is produced from 

 the egg. It is also noteworthy that the 

 greater number of cases of apogamy occur 

 in extremely variable species, such as the 

 crested varieties of different ferns (e. g., 

 Scolopendrmm vulgare var. ramulosissi- 

 mum). Professor Bower has also called 

 attention to the fact that these are all 

 forms belonging to the highly specialized 

 and relatively modern group of Leptospo- 

 rangiatffi. If apogamy is a reversion to a 

 primitive condition, it is strange that it 

 should occur in the least primitive ferns 

 rather than in the older types. 



I think we may fairly class the phe- 

 nomena of apospory and apogamy with 

 the numerous cases of adventitious groM'ths 

 so common among both pteridophytes and 

 seed plants. In these the whole sporo- 

 phyte may originate as a bud from any 



