SEED AND EOOT 



197 





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FIG. 249. DKYAD'S SADDLE (Polyporus squamost 



IE. Step. 



A Fungus parasitical upon various trees. Bach pileus is from sis inches to two feet across, of an ochreous ground 

 tint, more or less covered with fringed red-brown scales. 



Aerial roots, unless they are epiphytal, are usually more or less circular 

 in section, though they are liable to flatten out in growth if they are of the 

 nature of clinging or supporting roots. Parasitic roots offer more variety, 

 and may be rounded, flattened, wart-like, ribbed, disc-shaped, netted, etc., 

 according to the special character of their work and the peculiarities of 

 their environment. Some epiphytal Orchids, in addition to their white cord- 

 like hanging roots, have others of a strap-like form, which adhere so firmly 

 to the trunks of the host trees, that it has been found impossible to loosen 

 one of the straps without tearing away a portion of the bark. "In other 

 species of tropical Orchids," * says Kerner, "the roots are not flat from the 

 beginning, but become so when they come into contact with the bark. 

 A root is often to be seen which arises as a cylindrical cord from the axis, 

 then lays itself upon the bark in the form of a band, and farther on lifts 

 itself once more, resuming at the same time the rope form. . . . Complete 

 coalescence takes place between the bands and the bark, and the union is 

 extremely close." It is affirmed by the same writer that, when the seeds of 

 any of these tree-growing Orchids " are transferred to loose earth devoid 



* E.g. Sarcanthm rostratus. 



