THE AMERICAN NATURALIST. [Vol. XXXVII. 



from a group of oogonia. protected by sterile tissue, is a novel 

 one, but it is hard to see upon what evidence it is based. Of 

 the algal forms, the structure of the oogonium of the Characeae 

 resembles most nearly that of the archegonium ; but that this is 

 anything more than an analogy is questionable, and at present 

 it must be confessed that the origin of the archegonium is 

 extremely obscure. 



As to the significance of apospory and apogamy, both of 

 these phenomena may, I think, fairly be compared to the vari- 

 ous types of adventitious budding. We know that among both 

 ferns and seed-plants, adventitious shoots may arise from almost 

 any portion of the plant-body. The whole sporophyte may 

 develop as an adventitious bud upon the root, leaf, stem, or 

 even from the sporangium, shown by the budding of the nucel- 

 lus in several cases of polyembryony, or the replacing of the 

 sporangium by a shoot in Isoetes. Surely no morphologist 

 would claim that because in Camptosorus or Cystopteris the 

 sporophyte may arise as a bud upon the leaf ; or in Populus or 

 Ailanthus may spring as a bud from the root ; that these facts 

 indicate that such was the original origin of the sporophyte, 

 and that the latter is directly homologous with the organ from 



I think, therefore, that we must fall back upon the question 

 of water-supply as the real explanation of the peculiarities of 

 the leafy sporophyte. All mosses remain to a certain extent 

 aquatic, most of them absorbing water at all points much as an 

 alga does, and depending only to a limited degree upon the 

 rhizoids as a means of water absorption. Moreover the rhizoids 

 are entirely inadequate to supply a plant body of large size, 

 which could not, of course, absorb sufficient water for its needs 

 from the atmosphere. Nature has, apparently, made numerous 

 attempts to adapt the essentially aquatic gametophyte to a 

 terrestrial environment, with very imperfect success. 



The sporophyte, at first a purely spore producing structure, 

 has been from the beginning essentially aerial in habit, never 

 being directly in contact with water, but getting its water-supply 

 indirectly, at first through the cells of the gametophyte, but 

 soon developing a special massive absorbent organ, the foot, the 



