370 FERNS. 



delicate micrometer, are found to average not more 

 than 1 -20,000th of an inch in diameter, while many 

 are as low as l-50,000th. In G. clirysopJiyllum the 

 appearance of the gold-coloured dust is in general the 

 same ; but it is arranged more distinctly in corpuscles, 

 which stand up from the surface of the frond on 

 slender foot-stalks ; the whole not unlike tiny cauli- 

 flowers. Both heads and stalks are pellucid and 

 colourless, but are dusted all over, the heads most 

 abundantly, with fine sulphur-like granules, which 

 also lie scattered thinly over the ground between the 

 stalks. When scraped off with a needle, the granular 

 texture under a high power is scarcely manifest, the 

 substance forming coherent lumps, somewhat like a 

 very crumbly cheese. G. Martensii shows stalked 

 processes as the last ; but under a power of 600 dia- 

 meters these are less coherent, and composed, not of 

 granules, but of an infinity of slender short rods, 

 cohering in every possible direction, about 1 -20,000th 

 of an inch in thickness, and of varying length, straight 

 or variously curved, and translucent in texture. G. 

 Tartareum, the best of the silver ferns, is very white 

 beneath. Stalked processes are discernible, but few, 

 and almost, concealed by a profusion of downy silvery 

 spicules, looking like the finest hoar-frost on a blade 

 of grass. Under a power of 600 diameters, we find 

 fibrous transparent rods as before, but with much less 

 coherence, and resembling a spicular sponge after 

 passing through fire, or the deposit which remains 

 after a good deal of cutting of cloth, roughly brushed 



