HORNWORTS 



245 



(the sporophyte), whose interior cells divide into spores, 

 but there are no " elaters." Although still surrounded by 

 the distended archegone this sporophyte is not organically 

 connected with any part of the gametophyte. The spores 

 escape by the decay of the surrounding layers of cells, and 

 on germination give rise to gametophytes like that with 

 which we started. 



428. In the Homworts (Anthoceros) the gametophyte 

 is a thin thallus of somewhat more compact tissue than 

 in Riccia, and growing on moist earth. The antherids 



Fig. 118.— Riccia. 



Fig. 119, — Anthoceros. 



and archegones are sunken in the upper surface, and 

 resemble those of Riccia. When fertihzed the egg de- 

 velops into an elongated, cylindrical sporophyte whose 

 upper part emerges from the neck of the archegone, 

 while the enlarged base remains seated in the venter. 

 The sporophyte is made up of a considerable mass of 

 green tissue, and is surrounded by an epidermis which is 

 supplied with stomata like those of higher plants. This 

 is the first appearance of true stomata in the Vegetable 

 Kingdom. 



429. The lower part of the sporophyte continues to 

 grow in length indefinitely. Internally there is a layer 

 of cells by the division of which spores are formed, and 

 intermingled with these spores are the elongated sterile 

 cells called "elaters." As the spores ripen above the 

 sporophyte splits from the top to permit their escape. 



