298 



BOTANY. 



ascus (the so-called free cell formation). Usually there is a 

 considerable quantity of the unused protoplasm left over 

 after the ascospores are fully formed (Fig. 204. a, b, c). The 

 usual number of ascospores is eight (Figs. 202, 203, 204), 

 although in exceptional genera they range from one or two 

 ( Umbilicaria) to a hundred or more (Badrospora, and other 

 genera). They are frequently septate, sometimes being di- 

 vided into two portions e.g., Parmelia (Fig. 202) or 

 many, as in Collema Urceolaria, etc. In the gymnocarpous 

 lichens the ascospores escape directly into the air. and this 

 they generally accomplish with such force as to be projected 

 some millimetres ; in the aiigio- 

 carpous genera they first escape 

 into the cavity of the perithe- 

 cium, from which they pass out 

 through an opening in its apex. 



396. In germination the as- 

 cospore commonly sends out a 

 germinating tube, which is a 

 growth from the endospore ; it 

 develops directly into a hypha, 

 and becomes branched and sep- 

 tate. Bi- or multilocular asco- 

 spores usually send out a germi- 

 nating tube from each cell. In 



the s enera with ver y lar e asc - 



spores e.g. , Megalospora, Per- 

 tusaria, etc. the germination takes place in a way somewhat 

 different from that just described. In the endospore a 

 great number of cavities or canals form (g, Fig. 205), from 

 each of which there grows out a germinating tube (d, Fig. 

 205) ; these many tubes elongate into hyphae, and become 

 septate and branched (/, Fig. 205). 



397. In addition to the apothecia, with their contained 

 ascospores, there are other organs which contain bodies 

 which are probably reproductive in their nature. The 

 best known of these are the spermagonia (Fig. 202, A, .<?, 

 and Fig. 206), which are small cavities, usually found upon 

 the same thallu.s as the apothecia; they contain branched 



DeBar >' 



