POLYTRICHUM SEXUAL ORGANS 347 



Sexual Organs 



VI. Take a mature antheridium-bearing axis of 

 PolytTiclium, and dissect it with needles in a watch- 

 glass, keeping all the detached parts. Examine them 

 carefully with a lens, and observe the following 

 categories of organs 



1. The perigonial leaves, which are widened 

 laterally into very broad membranous wings, with a 

 clearly defined, central midrib. 



2. The white, club-shaped antheridia. 



3. The paraphyses, which will often be found 

 associated with the antheridia : some of them are 

 simply filamentous, others are more or less clearly 

 spathulate. 



VII. Cut median longitudinal sections ot a male 

 axis : mount in weak glycerine, and with a low power 

 recognize the several organs above described, and their 

 relative positions : note especially the antheridia in 

 the axils of the perigonial leaves. Observe under a 

 high power the structure of a single antheridium : it 

 consists of a short stalk, and a club-shaped body, com- 

 posed of (i.) a -wall a single layer of cells in thickness, 

 and (ii.) a central mass of cells of more or less clearly 

 cubical form : these are the spermatocytes or mother- 

 cells of the spermatozoids. 



VIII. Take fresh antheridium-bearing specimens of 

 Polytriclmm, after some days of dry weather (or keep 

 them rather dry for some days, carefully preventing any 

 access of water from above) : squeeze one of them 

 between the finger and thumb : the antheridia will 



