SPORES AND THALLIDIA. 



15 



The last division of plants wherein the spores are formed deep down in a tissue 

 is that of the Muscinese, which include Mosses and Liverworts. In these plants the 

 spore-producing generation consists of a cellular body, which has arisen from the 

 fruit, is usually seated on a stalk, and in shape is cylindrical, pyriform, or more or 

 less spherical (cf. figs. 191 8 > 4 > 7 > 8 - 15 ). We must here remark, by the way, that botanists 

 used formerly to look upon this sporogenous generation of the Moss erroneously 



Fig. 191. Mosses. 



i Polytrichum commune, the sporogonium to the left concealed by the cap, the sporogonium to the right exposed. The same 

 Mo? in an earlier stage of development. * Sporogonium of Polytrichum commune with its lid. * The same after the lid 

 has fallen off. Bryum ccespiticium. Sporogonium of the same Moss with its cap. 1 The same without the cap, but 

 with the lid still on. 8 The same after removal of the lid, showing the teeth (peristome). A piece of the peristome. 

 " Antheridia, Archegonia, and Paraphyses of Bryum ccespiticium. " Hylocomium splendens. ** Sporogonium of 

 Hylocomium splendens. 1S Andrcea rupestris with burst sporogonium. n Sphagnum cymbifolium, its spherical sporogonia 

 still covered by their lids in the left-hand specimen, is A single sporogonium of the same Moss. 1, , , ", 1* natural 

 size ; , *, , 1, , 12, is, is x 6; , x 150. 



as the fruit itself. The only structure rightly to be considered as the Moss-fruit is 

 that in which the embryo is produced as a result of fertilization. If afterwards a 

 new generation springs up from the embryo which has been formed in the interior 

 of the fruit, this generation cannot any longer be described as a fruit even in cases 



