488 



A TEXTBOOK OF BOTANY 



[Ch. XI 



The typical life cycle in true Mosses is illustrated in Figure 

 346. On the upright leafy stems, which are the gameto- 

 phytes, are borne the sporogonia, which are the sporophytes. 

 The latter consist of spore capsules at the summit of tall 



Fig. 346. — The life cycle of a Moss, mostly Polytrichum. 



Left, the plant ; X \. Next, above, the capsule, in vertical median 

 section, X 6, with spore and germinating spore, X 300, and a spore germi- 

 nated to a protonema bearing a bud from which develops the familiar leafy 

 plant, X 75. Below, archegonial shoot, X 2 ; with archegonium in section, 

 X 16, antheridial shoot, X 2, with antheridium, X 16, and single sperm cell, 

 X 600. Last, developing sporogonium, showing origin of calyptra from 

 enlarged archegonium. (After Dodel-Port, and other sources.) 



slender set^e ; and they are usually capped by the calyptra, 

 a loose conical cover which is a relic of the archegonium. The 

 spore capsule in the true Mosses is a highly specialized struc- 

 ture. At its base is a swelling, the apophysis ; at its tip is 

 a cap, the operculum, which falls off at maturity, released 



