GROWTH OF FUNGI. 43 



"Wheat Mildew, for instance, often arrives at a certain stage 

 of growth without perfecting its fruit, a fact whicli suJBfi- 

 ciently accounts for the apparently sudden appearance which 

 it makes in seasons favourable to its full development amongst 

 our crops. 



As regards the growth of individual Fungi, it takes place 

 essentially in a direction from the centre to the circumference, 

 or, in other words, it is centrifugal. Hence a Polyporus, such 

 as P. fraxineus, involves every stick and blade of grass in its 

 way as it increases in diameter. The mode of growth is ad- 

 mirably illustrated by a section of Polyporus hispidus, so 

 common on apple-trees, in which the threads of which it is 

 composed are seen to radiate in one direction towards the 

 pileus, where their free ends form the hispid fascicles on the 

 surface, and in another direction towards the hymenium, 

 where they form the walls of the tubes and sporophores. It 

 is not indeed intimated that no growth takes place in any 

 other direction, but that the main direction is centrifugal. 



Fungi are in general of short duration, but some go on 

 increasing for years. Polyporus fraxineus, though only a few 

 inches across, the first year, attains at length a breadth of as 

 many feet. Some of the stipitate Polypori scarcely attain 

 their full characters till the second year, and a few even of the 

 softer species, if they get through the winter, sprout again 

 from the portion of tissue which remains sound. In such 

 case, though at first the nutriment was derived from the 

 matrix, by means of the spawn which performs the functions 

 of roots, life is carried on by the absorption of surrounding 

 moisture, and perhaps partly at the expense of the dead 

 Fungi. Even some Agarics, as A. fusipes (Plate 5, fig. 5), 

 seem sometimes to sprout from the decayed stumps of the 

 previous year, without any fresh mycelium. 



