GERMINATION AND GROWTH. 153 



tpora rather than with the plants so long associated with it 

 amongst the Coniomycetes. 



In passing from, these to the 3fuccdincs, therefore, we cannot 

 do so more naturally than by means of that genus of vthite 

 moulds to which we have just alluded. The erect branched 

 threads bear at the tip of their branchlets spores, or conidia, 

 which conduct themselves in a like manner to the organs so 

 named in Gystopus, and oogonia or resting spores developed on 

 the mycelium within the tissues of the foster plant also give 

 origin to similar zoospores. 



The conidia are borne upon erect, elongated filaments, origi- 

 nating from the creeping mycelium. These threads are hollow, 

 and rarely septate ; the upper portion divided into numerous 

 branches, and these again are subdivided, the ultimate ramuli 

 each terminated by a single conidium. This body when mature 

 is oval or elliptical, filled with protoplasm, but there is a diver- 

 sity in their mode of germination. In the greater part, of 

 which P. ejfiisa may be taken as an example, the conidia have 

 the function of simple spores. Placed in favourable conditions, 

 each of them puts forth a germ-tube, the formation of which 

 does not differ in any essential point from what is known of the 

 spores of the greater part of fungi. 



The short oval conidia of P. gangliformis have little obtuse 

 papilla3 at their apex, and it is at this point that germination 

 commences. 



The conidia of P. densa are similar, but the germination is 

 different. When placed in a drop of water, under favourable 

 circumstances, the following changes may be observed in from 

 four to six hours. The protoplasm, at first uniformly distributed 

 in all the conidia, appears strewn with semi-lenticular, and nearly 

 equidistant vacuoles, of which the plane face is immediately in 

 contact with the periphery of the protoplasm. These vacuoles 

 number from sixteen to eighteen in P. macrocarpa, but are less 

 numerous in P. densa. A short time after the appearance of the 

 vacuoles the entire conidium extends itself so that the papilla 

 disappears. Suddenly it reappears, elongates itself, its attenu- 

 ated membrane vanishes, and the protoplasm is expelled by 

 8 .... 



