1896.] Vegetative Phase of the Sporophyte. 355 



the mass of sporongenous tissue was necessarily accompanied 

 by a sterilization of potential portions of the mass for purposes 

 of protection, support, and for the conduction of nutritive 

 material. From this condition he reviews the theoretical 

 grounds for the relegation of the spore-producing cells to a 

 superficial position, and the eruption of outgrowths on which 

 the sporangia are supported, citing as illustrations of the early 

 conditions of these outgrowths the strobilus of Equisetum and 

 Phylloglossum. From the latter he traces the development of 

 the elongated and branched leafy stem of species of Lycopod- 

 ium by continued apical growth of its strobilus, while the 

 sporangia on some of the lower sporophylls would be arrested, 

 and the sporophylls themselves would develop as foliage leaves. 

 For these and similar reasons elaborated by himself, he con- 

 cludes, rightly I think, that the sporophylls are, from a phylo- 

 genetic point of view, primary, while the foliage leaves are 

 secondary. 



All the evidence which we have points to the fact that in 

 the early development of the sporophyte, it was entirely de- 

 pendent upon the gametophyte for nutrition including the 

 supply of carbohydrates. The expanded green prothalloid 

 structure performed the same function for the sporophyte, that 

 foliage leaves of the sporophyte do in plants where this becomes 

 independent of the gametophyte. This is practically true now 

 in all the thalloid liverworts, and in all the Bryophyta is the 

 sporophyte practically dependent upon the gametophyte for 

 this function. In most of the Pteridophytes the sporophyte 

 is dependent upon the gametophyte for its carbohydrates dur- 

 ing the embryo stage. In some of the Pteridophytes, in the 

 Gymnosperms, and in the Angiosperms, the gametophyte has 

 entirely lost the function of carbon assimilation, this function 

 being solely performed by parts of the sporophyte. 



What influences led to the gradual transfer of this function 

 of the gametophyte to parts of the sporophyte ? Nutritive dis- 

 turbances have been shown to play a very important part in the 

 formation of sporophyllary organs quantitatively, in varying 

 ratios between the vegetative and sporophyllary structures 

 with increased food supply ; in a tendency to produce a natural 



