222 REPRODUCTION OF THE ASPERGILLALES 



history is suggestive of the algae. While conditions are favorable 

 for growth these plants are rapidly multiplied and disseminated 

 by conidia. Changed conditions cause the development of sexual 

 organs and the consequent formation of the gametospore. The 

 gametospore, however, does not become a resting spore as in some 

 of the green algae, but germinates at once, living on the parent 

 plant like a parasite just as in the case of the red algae. Note 

 also another resemblance, the gametospore first develops a mass 

 of cells, in this instance of a hyphal character, on which later 

 the spore-containing asci arise as lateral branches. 



Fig. 144. Further development of the ascocarp: A, sectional view, show- 

 ing the branches, s, derived from the germinating gametospore, that are 

 forming numerous lateral branchlets. B, one of the branchlets enlarged, 

 showing how it divides into cells which round off, forming the asci, as. C, 

 ascospore. D, germinating ascospore. — After Brefeld. 



The trufifles are a curious group of related fungi that live for 

 the most part entirely under ground. The mycelium of many 

 forms is supposed to live in contact with the roots of oaks and 

 other trees as a mycorhiza. The fleshy tuber-like ascocarp, often 

 as large as a walnut, is a highly prized delicacy in Europe where 

 dogs and pigs are trained to locate the truffles by smell. This 

 industry amounts to more than f 1,000, 000 annually in France 

 and Italy. 



