MUSCI AND HEPATICAE 



467 



of the main stem (acrocarpic), sometimes on short lateral 1 tranches 

 (pleurocarpic), and this character is useful in the classification of 

 Mosses. They are often protected by specially developed ' peri- 

 chaetial " leaves, which give an almost flower-like appearance (Poly- 

 trichum). In some Mosses the antheridia and archegonia are grouped 

 together, as in Meesia (Fig. 361) ; but commonly they are separate, 

 either on distant branches of the same plant (Funaria hygrometrica) , 

 or on different plants (Polytrichum, Buxbaumia). Their presence 

 upon the Moss-Plant makes it evident that it is the sexual generation, 

 or Gametophyte. 



Fig. 362. 

 i.-vi. Stages in development of the antheridium of Funaria hygrometrica, ziter 

 Campbell ( x 400). vii. Spermatozoids of Funaria, after Campbell, and Sachs. 

 ( x 800.) viii. Empty antheridium of Andreaea, with paraphysis, after Kuhn. 

 (* I35-) 



The analogy between the arrangement and distribution of the stamens and 

 carpels in the flowers of Angiosperms and the sexual organs in the perichaetia 

 of Mosses is obvious. But it must always be remembered that the two sides 

 of this comparison are essentially different. The antheridia and archegonia 

 of Mosses are the real sexual organs borne by the gametophyte, and they 

 contain the gametes ; the ovules and pollen-sacs of Angiosperms are parts 

 of the sporophyte, specialised so as to produce the highly modified gameto- 

 phytes, which in their turn produce the gametes. 



Both types of sexual organs project freely from the surface of the 

 plant. Each originates from a single cell, by a segmentation which 

 shows a continued apical sequence, and is quite distinct from that 



