THE COMMON "BRAKE." 67 



the ground. In this climate, however, it appears to be somewhat 

 undersized, for it grows to a height of fourteen feet in the Andes,* 

 and in Australia attains to twice the height of a man, forming 

 a dense undergrowth beneath tree-ferns 40-100 feet high.f In 

 Great Britain it is from six inches to nine feet high (Sowerby), 

 or even larger in exceptional cases. " In dry gravel it is usually 

 present, but of small size ; while in thick shady woods having a 

 moist and rich soil it attains an enormous size, and may often be 

 seen climbing up, as it were, among the lower branches and 

 underwood, resting its delicate pinnules on the little twigs, and 

 hanging gracefully over them."- (Newman.) 



GENERAL MOEPHOLOGT. 



The brake consists of two very different portions one green 

 and leaf-like, which rises above the ground ; the other black and 

 root- like, lying buried in the soil. These will henceforth be- 

 spoken of as the aerial and the underground parts. The latter- 

 lies at a depth of an inch to a foot below the surface, branching 

 widely in various directions. It may often be followed for a long 

 distance, and in such cases reveals a surprisingly complicated 

 system of underground branches. 



Superficially, the underground portion of the fern appears to 

 be a root, but a closer examination shows it to be reallv the stem 



* 



or axis of the plant, which differs from ordinary stems only in 

 the fact that it lies horizontally under the ground instead of ris- 

 ing vertically above it. The aerial portion, which is often taken- 

 for stem and leaf, is really leaf only. And the true roots are the 

 fine fibres which spring in great abundance from the underground 

 stem. Underground stems more or less like that of Pteris 

 are not uncommon occurring, for instance, in the potato, the- 

 Solomon's-seal, the onion, etc. In Pteris the stem is technically 

 called the rootstock or rhizome, and in this plant it constitutes the 

 larger and more persistent part of the organism. In the specimen 

 shown in Fig. 32 the rhizome was about eight feet long and bore 

 two leaves. It was dug out of sandy soil on the edge of a wood- 

 land, and lay from, one to six inches below the surface. It was 



* Hooker, I. c. 



\ Krone, Botan. Jahresbericht, 1876 (4), 846. 



