300 



BOTANY. 



398. — Until Stahl's researches* showed the existence of 

 sexual organs in Collema, they were entirely unknown among 



lichens. He discovered, deeply 

 imbedded in the tissue of the 

 plant, an organ composed of a 

 spirally coiled hypha- branch, and 

 a vertical septate portion, which 

 rises to, and projects above, the 

 surface; the spirally coiled por- 

 tion he called the ascogonium, 

 and the vertical portion the tri- 

 chogyne. The whole he regarded 

 as a species of carpogonium (Fig. 



smail portion of the thallus of Col^ nnry a „ „y,A J\ "pfp rvTioorvorl 

 lema Jacobctfolium, showing the '**J ') ^' '^J ^^^ "')• ^^ OOServea 



'^°hx^the 'Soc ile^" onidta^and^a spcrmatia adhering to the pro- 

 — : =..._,.-._ ....,=.v _i .---l:-.^ portion of the tricho- 



some of these united them- 



S06. — Vertical section of 



epermagoniuin, from which eperma- jectinff 

 tia are escaping. Magnified. — ^After ^ ° 



Tulasne. gjne : 



selves to the trichogyne by means of a tube (C, Fig. 207). 

 The result of this coalescence was the withering and disap- 

 pearance of the 

 cells of the tricho- 

 gyne, and the 

 growth and devel- 

 opment of the as- 

 cogonium. The 

 latter process takes 

 place as follows : 

 " The cells of the 

 ascogonium first of 

 all increase in size, 

 and then undergo 

 division ; as a re- 

 sult of this, the 



sniral ai-TaTio-Qw>Qv,+ ^' coalescence of a spermatiiim, S, wi( 

 bpirai arrangement a11 the figures magnified, B and (7 much 



of the cells be- -^^st*"- 



comes less an d less conspicuous, for the cells gradually sepa- 



* " Ueber die Qesclilechtliclie Fortpflanzung der Collemaceen," 1877 

 (On the Sexual Organs of the Collerancea;). A brief synopsis of Stahl's 

 results appeared in the Qr. Jour, of Mic. Science, October, 1878, 



-Sexnal organs of Collema mierophyllvm. A, 

 "--" — ~ - hyphse; 6, 6, the Nortoc-like 

 J, the exserted trichogyne. jB, 



Fi^. 207.- 

 section of thallus; a. a, 

 gonidia ; c. ascogonium; cf, 



the pperuiatia, 6, surrounding the exserted trichogyne, a. 

 C, coalescence of a spermatiiim, b, with trichogyne, a, 



more than A,— 



