480 PKACTICAL BOTANY 



cavity, and giving off at their apices by abstriction the 

 oval, motionless spermatia, which escape by a fine 

 ostiole. 



The escape of the spermatia may be observed in fresh 

 material, by mounting a piece of the thallus bearing 

 spermogonia in a drop of water, after it has previously 

 been kept dry for a time : the spermatia are then 

 extruded through the ostiole, embedded in a gelatinous 

 matrix. (Compare these spermogonia with those of 

 Puccinia.) 



VIII. Though the search for the female sexual organs 

 which precede the formation of the apothecia has been 

 successful only in few cases, still there is no great diffi- 

 culty in observing them in the genus Collema. Material 

 for this purpose should be collected in early spring 

 (March), and sections may be cut from it fresh, or better 

 after hardening in alcohol. Cut fine sections from a 

 part of a thallus which bears as yet no apothecia, let 

 them swell in water, or weak glycerine, and mount in 

 glycerine : observe here and there a fungal filament to 

 have become coiled at some distance below the sur- 

 face, and then to be continued almost directly to the outer 

 surface of the thallus, beyond which it projects this 

 coiled part is the ascogone, while the straight part is 

 the trichogyne. Occasionally spermatia are to be 

 seen attached to the apex of the trichogyne. 



In other sections apothecia may be seen in various 

 stages of development, or spermogonia having a structure 

 similar to that above described for Cetraria. 



