OOSPORA LACTIS 385 



decaying organic matter is Cladosporium herbarum, Link., 

 a conidial stage of some ascomycetous fungus. It fre- 

 quently produces dark olive-brown patches upon damp 

 paper, wood, barley, and other grains, dead leaves of all 

 kinds, and vegetable tissues generally. A form of it, 

 Cladosporium butyri, occurs sometimes upon rancid 

 butter (p. 354) and other dairy products. 



The hyphae, densely woven into a blackish-olive 

 stratum, often become divided into very short, almost 

 rectangular, lengths by transverse partitions, which pieces 

 may ultimately separate and germinate in the same 

 manner as a conidium or spore. 



The true conidia arise singly or in very short chains 

 of two or three members at the tips of sparingly branched 

 hyphae : they are at first pale in colour but later become 

 a dark olive-brown colour. In size and form they are 

 extremely variable, some of them being oval and others 

 oblong or cylindrical, usually smooth, simple, or with 

 one or two septa : most commonly they are oval, from 

 12 to 20 /A long and 5 to 8 ^ broad. 



Ex. 169. Procure and examine a specimen of Cladosporium 

 herbarum. 



Note the colour of the hyphae and their numerous septa. 

 Observe also the form and size of the conidia. 



4. Oospora lactis, Sacc. This organism, most com- 

 monly known by its earlier name Oidium lactis, Fres., 

 forms a snow-white velvety covering upon cream and 

 butter and on the outsides of many of the softer kinds 

 of cheese. The sterile hyphae are closely interlaced with 

 each other and spread over considerable areas when the 

 conditions for nutrition are suitable. In liquid media 

 they frequently break up into short lengths very closely 

 2 B 



