186 MUSCINE.E. 



Among the sexual organs, paraphyses filamentous or club- 

 shaped bodies are to be found. 



The asexual generation, the sporophyte (Moss-fruit or 

 sporogonium); As the result of fertilisation the oosphere sur- 

 rounds itself with a cell- wall, and then commences to divide in 

 accordance with definite laws. 1 The embryo (Fig. 189 G) pro- 

 duced by these divisions remains inside the wall a-a of the arche- 

 gonium (Figs. 190, 199 D, E), and developes into the sporogonium, 

 which remains attached to the mother- plant, often nourished by 

 it, as if the two were one organism. The lower extremity of the 

 sporogonium, the foot (Figs. 190 /; 199 _D), very often forces its 

 way deep down into the tissue of the mother-plant, but without an 

 actual union taking place. The central portion of the sporogonium 

 becomes a shorter or longer stalk (seta), while the sporangium 

 itself is developed at the summit. At a later stage, during the 

 formation of the spores, the sporangium very often assumes the 

 form of a capsule, and dehisces in several ways characteristic of the 

 various genera (Figs. 192, 193, 194, 195, 200). The basal portion 

 of the archegoninrn grows for a longer or shorter period, forming 

 a sheath, the calyptra, in which the capsule is developed, but 

 eventually it ceases to enlarge, and is then ruptured in different 

 ways, but, quite characteristically, in each group. Anatomically, 

 the asexual generation is often more highly differentiated than the 

 sexual ; thus, for instance, stomata are present on the sporangia 

 of the true Mosses, but are absent in the sexual generation. 



As the capsule developes, an external layer of cells the amphi- 

 thecium and an internal mass the endothecium are differ- 

 entiated. As a rule the former becomes the wall of the capsule 

 while the latter gives rise to the spores. In this Division, as in 

 the Pteridophyta, the name archesporium (Fig. 190 t) is given to 

 the group of cells inside the sporangium which gives rise to the 

 mother-cells of the spores. The archesporium is in general a 

 unicellular layer ; in Spliaijnum and Anthoceros it is derived from 

 the most internal layer of the amphithecium, but with these ex- 

 ceptions it arises from the endothecium, usually from its most 

 external layer. In the true Mosses and in liiccia only spore- 

 mother-cells are produced from the archesporium, but in the 



1 The oospore divides by a wall transverse or oblique to the longer axis of 

 the archegoniuni. From the upper (epibasal) cell, the capsule (and seta) is 

 derived, while the lower (hypobasal) gives rise to the/oo(. In Riccia the hypo- 

 basal half takes part in the formation of the sporangium. 



