174 



COMPARATIVE MORPHOLOGY OF FUNGI 



tion. This same manner of formation of conidia we will meet again in 

 the following order in the Erysiphaceae, only there the spore membrane 

 does not rupture. 



With the progress of the disease, the conidia disappear and there 

 appears on infected roots, a dark covering of brown, thick-walled gemmae 

 (chlamydospores) which arise catenulately and are liberated as the 

 hyphae disintegrate (Fig. 108, 3). Later, when the roots are dead, there 

 appear shining black perithecia whose ontogeny and whose connection 

 with both imperfect forms has not been experimentally investigated. 



While the Thielavia group shows a strong development of conidial 

 apparatus, this reaches its maximum in the third line, the Aspergillus- 

 Penicillium group. The representatives of this group are cosmopolitan 

 and the most common of all fungi. In them, also, various groups of 



Fig. 108. — Thielavia basicola. 1. Young conidiophore before the formation of the first 

 conidium. 2. Older stage. The left branch has formed the wall of the first conidium; the 

 basal cell is again binucleate. The right branch shows the first conidium leaving the 

 sheath. 3. Chlamydospores. ( X 500; after Brierly, 1915.) 



species vary in their ecological characters. Thus the true species of 

 Penicillium occur in forest floors, more rarely on cultivated, manured 

 ground as mesosaprobes on which bacteria preponderate. In forests they 

 are more important than the Mucoraceae, and by the digestion of hemi- 

 celluloses play an important role. In addition, they occur in temperate 

 climates on garbage and offal. In the tropics, the species of Aspergillus 

 predominate and there colonize everything possible. 



Many species of this group are technically important on account of 

 their hydrolytic powers on starch, sugars and tannins and cause fermenta- 

 tions to oxalic, citric, and gallic acids, more rarely to alcohol, as Asper- 

 gillus Oryzae which is used in Japan in the preparation of sake (rice wine) 

 and soy bean sauces by the hydrolysis of starch. In America, the 

 diastase from this organism is widely used instead of malt diastase in 

 industry; Aspergillus Wentii, by the loosening of the hard tissue of the 



