DEVELOPMENT OF PLANTS 243 



formed into asci as shown in Fig. 154, A, B. The ascoearps 

 finally decay and 'set free the ascospores which develop a new 

 plant or mycelium. Thus the entire life history in these forms 

 as in other fungi is suggestive of the algae. While conditions are 



Fig. 153. Sexual reproduction of the Aspergillales and the formation of 

 the ascocarp or perithecium: A, meeting of the male, an, and female, o, 

 gametangia. B, early stage in the development of the ascocarp. The gamet- 

 ospore has formed a series of branches, s, which are being surrounded by hyphae 

 (unshaded in the figure) from the mycelium. C, later stage seen in section. 

 The gametospore has formed a much-branched body, s, which is surrounded 

 by a closely interwoven mass of hyphae that appear in section as c^lls. — 

 After Brefeld. 



favorable for growth these plants are rapidly multiplied and dis- 

 seminated by conidia. Changed conditions cause the develop- 

 ment of sexual organs and the consequent formation of the game-' 

 tospore. The gametospore germinates at once, living on the 

 parent plant like a parasite just as in the case of the red algaie.' 

 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. 



The truffles 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 Fraiice 

 and Italy. 



