—ii4— 



below. Among tufted fronds, such forms are the rule. 

 All the lower pinnae are sometimes equally and extremely 

 reduced, the largest ones being immediately above these. 

 Such fronds are physiologically like those with long stipes 

 and large lowest pinnae. Fronds with broad bases which 

 are so placed as not to overlap might lose considerable 

 light between the stipe, but in general this space is util- 

 ized. A v long, broad wing on the stipe sometimes extends 

 the assimilating area. In many species the lowest pinnae 

 are deflexed forward so that they practically fill the 

 space between the frond bases. Deltoid fronds usually 

 reach the same end by a strong basicopic development 

 of the lowest pinnae. Since half the margin of the frond 

 is longer than its axis, most pinnae being narrowed 

 toward their apices lose considerable space between their 

 distal ends. This form economizes the conduction of 

 water and food and is mechanically good because it is 

 compact, but it involves a waste of light which is saved 

 in Nephrodinm> diversUobmn and N. Bordeni, which 

 broaden toward almost truncate apices. The pinnae, as 

 well as the fronds of ombrophilous plants, as is to be 

 expected, are in general fitted together so as to utilize 

 all possible light consistent with the disposible surface. 

 Notably perfect mosaics are presented by Davallia solida, 

 Dennstcedtia William si and all fronds with trapezoidal or 

 lunulate pinnae or pinnules. The pinnae of Lindsaya pul- 

 chella would overlap wastefully were they not set at such 

 an angle that they act like a grating. 



Perhaps the most interesting specialization of the roots 

 of ferns, but one which I have seen mentioned nowhere 

 else, is the massing of very numerous roots, all densely 

 covered by a felt of long, brownish, persistent root-hairs 

 which form a structure for the storage of water. Ap- 

 propriate to their function, these masses of* hairy roots 

 are commonly found on ferns growing on naked rocks 

 or tree trunks, but never on ferns with abundant soil nor 

 on trunks laden with moss. Persistent root-hairs as 



