GENERATION OF FUNGI. 



343 



and it may be fairly surmised that these sporules remain dor- 

 mant, unless an unfavorable season should favor their develop- 

 ment, by inducing an unhealthy condition of the vsrheat-plant. 

 The same general doctrine probably applies to the Botrytis, which, 

 from 1847 to the present time, has had a large share in the pro- 

 duction of the "Potato-disease;" and to the Oidium, which has 

 a like relation to the "Vine-disease" that has been extending 

 itself for some years past through the south of Europe. There 

 seems no doubt that, in the fully developed disease, the Fungus 

 is always present ; and that its growth and multiplication have a 

 large share in the increase and extension of the disorder, just as 

 the growth of the Yeast-plant excites and accelerates fermenta- 

 tion, and its reproduction enables this action to be indefinitely 

 extended through its instrumentality. But just as the Yeast- 

 plant will not vegetate save in a fermentable fluid, that is, in a 

 solution which, in addition to sugar, contains some decomposable 

 albuminous matter, — so does it seem probable, on a consideration 

 of all the phenomena of the Potato and Vine diseases, that 

 neither the Botrytis of the one, nor the Qidium of the other will 

 vegetate in perfectly healthy plants ; but that a disordered con- 

 dition, induced either by forcing and therefore unnatural systems 

 of cultivation, or by unfavorable seasons, or by a combination of 

 both, is necessary as a "predisposing" condition. 



213. In those lower forms of this class to which our notice of 

 it has hitherto been chiefly restricted, there is not any very com- 

 plete separation between its nutritive or vegetative, and its Ee- 

 productive portions ; every cell, as in the simplest Protophytes, 

 being equally concerned in both. But such a separation makes 



Fig. 126. 



.^eidium tussiloffinis : — a, portion of the plant magnified; b, section of one of the conceptaclefl 

 with its spores. 



itself apparent in the higher ; and this in a very curious mode. 

 For the ostensible Fungi of almost every description (Fig. 126) 

 consist, in fact, of nothing else than the organs of fructification ; 



