422 BOTANY OF THE LIVING PLANT 



commonest are readily distinguished by their stature and colour. 

 Low-growing, velvety, blue-green patches are Penicillium crustaceum ; 

 coarser, olive-green patches, with mop-like heads, of size visible 

 tc the naked eye, are Eurotium (Aspergillus) herbariorum. As the 

 patches of the latter grow older, minute yellow specks may appear 

 upon them : these are the Eurotium-irmts, a stage originally described 

 as a distinct fungus. A breath will carry away the numerous conidia 

 from such a culture in a dense cloud. They form part of the ordinary 

 dust of dwellings, and this accounts for the constant appearance of the 

 Moulds on organic substrata where the conditions are favourable to 

 heir growth, as in the moist air in a close cupboard, or under a bell-jar. 



Fig. 320. 



Conidiophores of Eurotium herbariorum (to the left) and of Penicillium crustaceum 

 (to the right). (From Strasburger.) Highly magnified. 



If a sample of Eurotium be taken, the branched and septate my- 

 celium is seen to ramify over and penetrate into the organic sub- 

 stratum, deriving nourishment till able to propagate. Stout branches 

 then rise upright as conidiophores, which swell upwards into a spherical 

 head (Fig. 320). On this numerous conical sterigmata bud forth, each 

 giving rise to a chain of conidia, formed in basipetal succession. The 

 oldest is distal, and successively others are abstricted off : an arrange- 

 ment which provides for the due nourishment of each, and the ready 

 removal of those that are mature by any breath of air ; for these 

 minute polynucleate conidia are very lightly attached. They 

 germinate readily in water or damp air, and the mycelium permeates 

 any nutritive medium ; thus they serve for the quick spread of the 



