10 



THE FERN BULLETIN 



The name frond was early given to the leaves of 

 ferns and will probably always be used in designating 

 these structures, but strictly scientific botanists are in- 

 clined to divide them into two groups according to the 

 work they perform. Thus the ordinary leaves are 

 called such while those which bear the asexual spores 

 are known as sporphylls. In the ferns the sporophylls 

 are usually very much like the leaves in appearance, 

 but among the fern allies may be seen a gradual dif- 

 ferentiation between them until in such plants as the 

 Lycopodhnm and Selaginellas the sporophylls are set 

 apart for the work of spore-production while the 

 leaves are devoted to purely vegetative functions. In 

 Lycopodium the sporophylls are borne at the tip 

 of a branch, forming the familiar spike, and each 

 sporophyll produces the same kind of spores. In 

 Selaginella, however, there are two sizes of spores, the 

 smaller being borne in the axils of sporophylls near the 

 tip of the spikes, while the larger are borne on the 

 sporophylls below them. The sporophylls bearing the 

 large spores are the mcgasporophylls and the other are 

 microsporophylls , the sporangia that enclose the spores 

 being known as mcgasporangia and microsporangia, 

 respectively. This condition also exists in Isoctes, 

 but in Marsilia, where there are two sizes of spores, 

 both are borne on the same sporophyll which is folded 

 up, somewhat like the pinnules of Onoclca. forming a 

 sporocarp. 



It is often asserted that the sex-organs of the pro- 

 thallium are homologous with the stamens and carpels 

 of flowering plants, but from the foregoing it may be 

 seen that this it not correct for the pollen grain is 

 really a spore. The stamens and carpels have their 

 c< >unterparts among the ferns it is true, but it is among 



