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 (c/. figs. 1 91 ^' ■•■ "■ ^' ^^). We must here remark, by the way, that botanists 

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



Fig. 191.— Mosses. 



1 Polytrkhum commune, the sporogoniuni to the left concealed by the cap, the sporogonium to the right exposed. 2 I'he same 

 Mo?s in an earlier stage of development. 3 Sporogoniuni of Polytrichum comviwie with its lid. * The same after the lid 

 has fallen i>ff. s Dryum ccespiticium. 6 .Sporogoniuni of the same Moss with its cap. ^ 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. 

 10 Antheridia, Archegonia, and Paraphyses of Bnjujn ccespiticimn. n Hylocomium splendens. 12 Sporogonium of 

 Uylocuiniutn splendens. ^^ Andrcea rupestris with burst sporogonium. i* Sphaynujn cytnhifoliuin, its spherical sporogonia 

 still covered by their lids in the left-hand specimen. 15 \ single sporogonium of the same Moss. 1, -, s, n, 1* natural 

 size ; ', *, «, ', », >2, i», " x 5; ', i" 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 embiyo which has been formed in the interior 

 of the fruit, this generation cannot any longer be desci'ibed as a fruit even in cases 



