8 



THE FERN BULLETIN 



do but to consider tho-;e peculiar fern parts that climb 

 to the tops of the trees as leaves, also. There are 

 several reasons, however, why we are justified in refus- 

 ing- them this title. No matter what the situation at 

 present, it is certain that stems and fruiting parts came 

 before real leaves. The leaf is essentially an expanded 

 part of the stem designed to facilitate the work of car- 

 bon-assimilation. True leaves, as we know them, 

 originated among the ferns and it is to be assumed that 

 for a time they would assume more or less of the char- 

 acters of both stem and leaf, but the evolution is always 

 from stem to leaves not the reverse. Thus we find that 

 it is not impossible to induce young sporophylls to take 

 on leaflike parts as in the "obtusilobata" forms of 

 Onoclca and Struthioptcris, while otherwise normal 

 leaves may on occasion produce sporangia. As if to 

 bear us out in the contention that the so-called fronds 

 of Lygodium are not real leaves, we find frequent indi- 

 cations of buds on the pinnae. The production of buds 

 is a strongly emphasized characteristic of the stem and 

 while it is well known that many leaves, even those of 

 flowering plants may originate buds, they usually do 

 not do so except under extraordinary circumstances. 

 Another stem-like character of Lygodium "fronds" is 

 the fact that there is no limit to the size they may at- 

 tain, while in normal leaves no such varying stature 

 is usual. It may not be possible to prove beyond 

 question that the aerial parts of Lygodium are stems, 

 but it seems much more logical to consider them se- 

 condary stems, and the so-called pinnae as leaves. In 

 a similar way it is permissible to call the above- 

 ground part of the < dder's-tongue a spore-bearing 

 stem with an expanded green portion performing the 

 offices of a leaf. It is out of the question to view these 



