No. II.] THE BRYOPHYTES OF CONNECTICUT. II 



sporophyte which remains in close contact with the gameto- 

 phyte usually forms a special absorbing organ, or foot. This 

 organ, however, never acquires the power of absorbing from 

 the outside, so that the sporophyte is never able to exist as 

 an entirely independent plant. 



The spores are borne within a closed case, or capsule, 

 which constitutes the so-called fruit in the Bryophytes. The 

 capsule is bounded on the outside by a sterile wall, and the 

 space in which the spores are developed is known as the 

 spore cavity. When the spores are mature, they lie loose 

 within the cavity, and are set free by the rupturing of the 

 wall. In the majority of cases the capsule is borne on a 

 slender cylindrical stalk, which connects it with the foot and 

 at the same time lifts it above the gametophyte. 



When the fertilized tgg begins to divide, the sterile cells 

 which form the wall of the venter also undergo divisions and 

 develop into a protective covering for the young sporophyte. 

 This covering is called the calyptra, and for a considerable 

 period its growth keeps pace with that of the sporophyte. 

 Sooner or later, however, it ceases to enlarge and is eventually 

 ruptured by the swelling capsule. The neck of the fertilized 

 archegonium plays no part in the development of the calyptra, 

 but can frequently be detected at its apex in a shriveled condi- 

 tion. In a few specialized genera a true calyptra is not formed. 



Upon germination a spore at first gives rise to an embryonic 

 structure, or protonema, upon which the characteristic gameto- 

 phyte afterwards develops. The protonema is sometimes 

 very short-lived, but in many species persists for a considerable 

 period. It usually consists of a copiously branched filamentous 

 structure, but it may be composed of a flat layer of cells or 

 of a small solid cell mass. In some cases the protonema is 

 represented by a very few cells arranged in a simple cell row 

 and is then scarcely distinguishable. 



Although very few Bryophytes are truly aquatic, it has 

 been shown that the presence of water is necessary for the 

 process of fertilization. It not only enables the antheridia and 

 archegonia to open, but it also affords a medium in which 

 the motile sperms can swim. The water is usually supplied 

 by rain, but, if no rain falls at the proper time, the antheridia 

 and archegonia gradually shrivel away and sporophytes fail to 



