139 



the seta. In this capsule are produced the asexual spores. As 

 the embryo develops in the archegonium, the wall of the latter 

 is stretched and eventually ruptures, a portion of the torn 

 investment being carried up on the capsule, as the seta 

 elongates, and thus forms the cap, or calyptra. The capsule is 

 usually closed, until ripe, by a lid called the operculum and a row 

 of minute teeth, called the peristome, is often found fringing the 

 upper edge of the capsule inside, just below the operculum. 

 We thus see that there are two distinct stages in the life -history 

 of a moss, the general form and appearance of the plant varying 

 considerably in the two stages. There is thus the sexual stage,, 

 the ordinary moss -pi ant, which arises from the asexual spore 

 and produces the sexual reproductive organs. As a result 

 of the sexual process of fertilisation, the oospore is formed, and 

 with this commences the asexual stage which ends with the 

 production of asexual spores. Each of these stages is called a 

 generation, and when they alternate regularly, as in the moss^ 

 the phenomenon is termed an alternation of generations. The 

 sexual generation is called the Oophyte, or Egg-plant, and the 

 asexual the Sporophyte, or spore-plant. The former arises from 

 a spore produced asexually, the latter from a spore produced 

 sexually. The life-history of the moss may be shortly expressed 

 as follows : 



Sporophyte Oophyte 



Spore ^-Protonema 



I 

 Moss Plant 



c? antheridia $ archegonia 



! I 



spermatozoid = oosphere 



! 



Sporogonium^ -oospore 



124. We now come to the third Pterido- 



and last great group of cryptogams, viz. the PTERIDOPHYTA. P^* 63 - 

 The plants in this group exhibit a distinct differentiation 

 into root, stem and leaves and possess true vascular bundles, 

 while in the case of these plants, as in the Bryophyta, Ferns, 

 there is a distinct alternation of generations. The plants 

 of most forest importance included in this group are those 

 known as the Ferns (Filices). The leaves of ferns are called 

 fronds, their venation is usually furcate and their vernation 

 circinnate. The young stem and leaf-stalks are usually 



