ASPERGILLUS. 193 



which is thus finally covered with a thick head of radially- 

 arranged chains of conidia. These masses form the greyish- 

 green dust which covers the mycelium. 



Finally, the conidia separate, and then have a warty 

 appearance on their outer surface. These small bodies can 

 germinate (p) as soon as they are detached, and at once develop 

 a new mould ; upon this fact depends the rapidity with which 

 the plant spreads. Under certain conditions, which are not 

 yet sufficiently known, but in every case appear to be con- 

 nected with a free supply of nutriment, the fungus develops 

 perithecia. They appear at first as tender branches, which, 

 at the termination of their longitudinal growth, begin to twine 

 their free ends in the form of a spiral of four to six turns (/) ; 

 the threads of the spiral gradually approach nearer together, 

 until finally they come into contact, so that the whole end of 



Fig. 34. Euroti'jm aspergiUuit glaitcug (de Bary). m. m, hyphal thread, carrying a conidio- 

 phore c (from which the conidia have fallen), a perithecium F, and the first rudiments of an 

 ascogonium, / ( x 190) ; , three sterigmata from the crown of a conidiophore, showing the 

 couidia-constrictions ; p, germinating conidium (x 250-300); A, Ascus; r, germinating asco- 

 spore ; k, germ tubes ; S, spiral ascogonium ; at p the commencement of the growth of one of the 

 enveloping hyphac ; T, older stage ; W_, ascogonium, already surrounded by the envelope ; V, 



gonium is enveiopea in a sneainoi many layers; 11 nas loosened us convolutions, ana is DagmiuDg 

 to throw out the ascus-forming branches ; M, portion of an older ascus-bearing branch ; a, a 

 young ascus ; a,, an older ascus which has burst. 



the filament takes the form of a helix (the ascogonium). Two 

 or more small branches which cling closely to the spiral then 

 grow from the lowest turn of the helix. One of these (S, T, p) 

 quickly outstrips the others in growth ; its upper extremity 

 reaches the uppermost turn of the helix, and fuses with it. 

 The other branch or branches likewise grow upwards along 

 the spiral, shoot out into new branches, and gradually become 

 so interlaced that the spiral is finally surrounded by an un- 

 broken envelope (W). These branches divide slowly into 

 septa perpendicular to the surface, and the envelope conse- 

 quently consists of short, angular cells, in which new septa 

 appear parallel to the surface, so that the envelope thickens 

 and is composed of many layers (V, X, F). The small sphere 

 now formed is about 0-25 mm. in diameter ; the outermost 

 layer is at first yellow and then brown ; the inner layers 

 remain soft, and are finally dissolved. After a time the spiral 



13 



