286 



BOTANY. 



ogonium by the growth of many basal enveloping branches, 

 and inside of this the carpogonium increases in size, and 

 sends out branches, which finally produce eight-spored asci. 

 The little tuber-like mass thus formed is yellowish, and of 

 the size and appearance of a coarse sand grain. 



(a) Aside from PenicilUum, we have in this country very few repre- 

 sentatives of this order. Two or three species of Tuber have been 



recorded, and two of Elaphomy- 

 ces.* 



(b) In Europe, where they grow 

 abundantly, Tuber cestivum, T. 

 metaiiospoium, and T. magnatum 

 are gathered for food. They are 

 found liy the aid of dogs and pigs, 

 which are trained to search for 

 them. 



379. — Order Helvellacese 

 (or Discomycetes). These 

 are for the most part disc-like 

 or cup -like saprophytes, 

 which frequently attain large 

 dimensions. The hymenium 

 is spread over the upper and 

 generally exposed siu'face of 

 the full-grown plant, which 

 is in reality the sporocarp. 



In Peziza, one of the prin- 

 cipal genera, the sexual or- 

 gans occur on the mycelium 

 on or in the ground ; the 

 ends of certain hyphae swell 

 up into ovoid vesicles, the carpogonia (Figs. 194 and 195), 

 each of which is provided with a more or less bent and 

 curved appendage, the trichogyne (Fig. 195, and /, /, Fig. 

 194). From below the carpogonium a branch grows out, 

 and, curving around, becomes closely applied by its tip to 

 the extremity of the trichogyne (Figs. 194 and 195). The 



Fig. 194.— Semal organs of Pcsiso eon- 

 fiuRiis^ hii^hly magnified. A, at time of 

 fertilization; a, carpogonium ; /, tricho 

 grne ; i, antiicridiuiD. B, after fertiliza- 

 tion ; A, A, the hypliae from which the re- 

 ciptucle is developed.— After Tulasne. 



* See Bulletin of the Torrey Bo'anieal Glub, November, 1878, for the 

 species of Tuber discovered in North America. 



