CRYPTOGAMIA FUNGI. 203 



change of colour frequently happens when there is no evi- 

 dent uredo, probably the result of an imperfect evolution. 

 GREVILLE. 



33. Jlf, Labiatarum, spots small, circular, dark brown, scattered, 

 encircled by the ruptured epidermis ; capsules globular, brown, 

 minutely pedicled HOOK. Scot. ii. 15. GIIEV. Fl. Edin. 436. 



Hab. On the leaves of Ajuga reptans in autumn. 



34. U. Ficaria, spots very dark brown, rather large, pulveru- 

 lent ; raised; capsules oval. GREV. Fl. Edin. 434. 



Hab. On leaves of pilewort in woods, not uncommon. 



**** Colour black. 



35. U. segetum, within the fruit and glumes of corn and grasses, 

 spreading, and in a short time filling the whole with a profuse 

 black scentless dust ; capsules minute, spherical. HOOK. Scot. ii. 

 15. GREV. Fl. Edin. 443. U. carlo. JBot. Gall. ii. 901. 



Hab. Grains of wheat, oats, and barley. 



This is, I believe, the Slack-ball of farmers. The injury it 

 does to the crops, although estimated to be very consider- 

 able by botanists, is in reality very trifling ; and the dis- 

 ease can be almost entirely prevented by proper pickling. 



LINNAEUS at one time was inclined to believe in the animal 

 nature of the fungi, and he seems to have been led to this 

 opinion by some observations on Uredo segetum. " With 

 regard to fungi," he writes to Ellis, u you may pick up, in 

 most barns or stacks of corn, spikes of wheat or barley, full 

 of black powder, which we call ustilago, or smut. Shake 

 out some of this powder, and put it into tepid water, about 

 the warmth of a pond in summer, for three or four days. 

 This water, though pellucid, when examined in a concave 

 glass under your own microscope, will be found to contain 

 thousands of little worms. These ought first to be obser- 

 ved, to prevent ocular deception. In mould, Mucor, you 

 will find the same, but not so easily as in the large fungi. 

 If, in the course of from 8 to 14 days, the water has been 

 kept up to the same temperature, you may observe how 

 these minute worm-like bodies become fixed, one after the 

 other, and acquire roots." LIXN. Corresp. \ 767. This is 

 very much like the process which has been observed in the 

 growth of some Contervae, and which has given origin to 



