394 



BOTANY 



PART II 



the uninucleate terminal cell (/<) and the stalk-cell (s) which also has a single 

 nucleus. The two nuclei of the young ascus fuse ((7), and the resulting nucleus 

 gives rise by repeated division to the nuclei of the eight ascospores (Z)). 



The highest development is exhibited by the peculiar fructifications of the 

 Helvellaceae, whose mycelium grows in the humus soil of woods. In the genus 

 Morchella (Fig. 335), the fructifications consist of a thick erect stalk, bearing a 

 club-shapeil or more or less spherical cap or pileus, which bears the hymenium, 

 with its eight-spored asci, on the reticulately indented exterior surface (Fig. 327). 

 The Morchellas are edible ( ta ), in particular M. csculenta and M. conica. The former 

 has a yellowish-brown cap, ovately spherical in shape, and attains a height of 

 12 cm. ; the cap of the latter is conical and dark brown, and it reaches a height 

 of 15 cm. Gyromitra esculenta, with dark brown cap and white stalk, and others 

 are also edible. In their external appearance the fructifications of these highly 

 developed Disromyretes greatly resemble those of the Basidiomycetes. 



Order 3. Pyrenomycetes ( 4 "- 4: ') 



The I'yrenomycetes comprise an exceedingly varied group of Fungi, some of 

 which are parasitic upon different portions of plants, particularly on the cortex 

 and leaves, and others are saprophytic upon decaying wood, dung, etc., while a few 



genera occur as parasites upon the larvae 

 of insects. The flask -shaped fructifica- 

 tions or perithecia are characteristic of this 

 order. The perithecia are open at the 

 top, and are covered inside, at the base, 

 with a Irymenial layer of asci and hair-like 

 paraphyses (Fig. 336). The lateral walls 

 are coated witli similar hyphal hairs, the 

 periphyses. The aseospoivs e>eape from 

 the perithecia through the aperture. In 



Fio. 336. Peritheciuni of l'odosporajlin't*f<lti 

 in longitudinal section. s, Asci ; a, 

 paraphyses ; e, i>eriphysps ; m, mycelial 

 hyptiH-. (After v. TAVF.L, x 90.) 



Fio. 337. 7, Coniiliophcn- alisti ictinx conulin. 

 from a pyenklinni of ' c///''"*/""'' hypodenni'i. 

 (After BREFKI.D, x 300.) S, Pycnirliiim of>7riV- 

 g <>/,<lin;'ni in vertical section. (Aft>T 

 TULASSK. x 70.) 



this process one ascus after another elongates in consequence of the water absorbed. 

 and ejects its spores through the opening, or the sj>ores are set free within the 

 peritliecia. and are pressed out, embedded in a swollen mass of mucilage. 



The simplest Pyrenomycetes possess free perithecia (Fig. 336) which are usually 



