DEVELOPMENT OF PLANTS 211 



of the gametes is made possible through a dissolution of the 

 separating walls at the tips of the gametangia. The gameto- 

 spore in germinating, develops an irregular hyphal outgrowth 



FIG. 143. Sexual reproduction of tlTe 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 

 gametospore has formed a series of branches, s, which are being sur- 

 rounded by hyphae from the mycelium. C, later stage seen in section. 

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

 rounded by a closely interwoven mass of hyphae that appear in section as. 

 cells. After Brefeld. 



(Fig. 143, B, .s) which becomes completely overgrown by the 

 hyphae of the mycelium (Fig. 143, B, C), thus forming a solid 

 body, known as the ascocarp or perithecium (plu. perithecia), that 

 appears to the eye as a minute grain of sand. During this growth 

 numerous lateral branches arise on the hyphae derived from the 

 gametospore and become transformed into asci as shown in Fig. 

 144, A, B. The ascocarps finally decay and set free the asco- 

 spores which develop a new plant or mycelium. Thus the entire 

 sexual process, with the exception that the male gamete is not 

 set free, is suggestive of the Rhodophyceae. 



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 



