POLYTRICHUM SEXUAL ORGANS 183 



Sexual Organs 



VI. Take a mature antheridium-bearing axis of Polytrichum, 

 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 of 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 antheri- 

 dium : it consists of a short stalk, and a club-shaped body, 

 composed 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 sperxna- 

 tozoids. 



VIII. Take fresh antheridium-bearing specimens of Poly- 

 trichtim^ 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 thus be easily forced from their position, and 

 may be mounted in water. If they were properly mature, it 

 may then be seen that on contact with water the antheridia 

 burst, and the spermatocytes escape, aggregated in a mass. In 

 each cell of this mass a spiral filament may be seen, in active 

 movement : ultimately it will escape, owing to mucilaginous 

 swelling of the wall of the mother-cell, as a free spermatozoid 

 of spiral form, having two cilia. 



IX. Take a sod of Funaria l with no sporogonia as yet visible 



1 Since Funaria hygrometrica produces sporogonia at all times of the year, and 

 is very common, while Polytrichum commune is reproduced sexually only in the 



