80 



THE FERN BULLETIN 



ling and readily identifies it. The young leaves, them- 

 selves are very characteristic the first being almost 

 round and others running through heart-shaped and 

 triangular forms. 



There are few ferns that show so unmistakably the 

 general pattern of the frond and the method by which 

 it is built up. Taking the young leaves we find the 

 heart-shaped forms with larger and larger basal lobes 

 until one more step makes the basal lobes independent 

 pinnae. Then the terminal pinnule and the two laterals 



go on developing large basal lobes until new pairs of 

 pinnae are produced. The logical outcome of all this 

 would be to make a strictly ternate frond, 

 and we may explain ternate species in some 

 such way, but in the cliff brake, the impulse 

 to grow at the tip is greater than that to grow 

 laterally, so the mature frond is much longer than 

 wide. Something of this same impulse seems to be 

 felt in the mature pinnae and pinnules themselves, for 

 they are commonly much longer than wide. 



The fully developed cliff brake is a thick and 

 leathery species, well adapted to endure the heat and 

 drouth upon the rocks i A selects as a home. The young- 

 leaves are, of course, very much thinner and more 

 delicate but they nevertheless always have a more sub- 

 stantial look than the other sporelings with which we 

 are acquainted. 



