33» 



PART IV. — VEGETABLE TAXONOMY. 



cell-mass thus formed penetrates the tissues of the parent plant, 

 and the rest develops outward, stretching, and finally rupturing 

 the walls of the archegonium, which, immediately after fertiliza- 

 tion, usually increases considerably in size, and then stops grow- 

 ing, while the sporogonium continues its development. As this 

 proceeds, the basal part usually develops into a stalk, sometimes 

 of considerable length, while the apical portion swells into a 

 capsule, which produces in its interior multitudes 

 of minute spores. See Fig. 546. 



The archegonium, in some species, is ruptured 

 at its apex by the growth of the sporogonium, and 

 then its torn remains are seen as a kind of sheath 

 at the base of the stalk j in others, and more com- 

 monly, it ruptures near the base, and then is borne 

 like a cap, called the calyptra, at the top of the 

 capsule. See Fig. 541, a. 



The capsules, when ripe, differ 

 in structure and mode of dehis- 

 cence, in ways which are more or 

 less characteristic of the genera. 

 In some, there is developed in the 

 interior of the capsule an axial 

 organ, called a columella, around 

 which the spores are borne (See 



Fig. 546. 



Fig. 547. 



Fig. 546. — Development of sporogonium of Funaria hygrometrica. a, archogonium 

 already much stretched by the development of the sporogonium, j, the lower part of which 

 has penetrated the tissues of the stem, and the upper part of which carries the calyptra, c. 

 Magnified about 50 diameters. After Sachs. 



Fig. 547. — Capsule of Phascum muticum cut open so as to show the columella, c, to 

 which a few spores are still attached. Magnified. 



Fig. 547) ; in others, no such organ is present, xn the capsules 

 of some there are developed among the spores peculiar fila- 

 mentous, usually spirally coiled, bodies, called elaters, which aid 

 in the ejection of the spores after the capsules are ripe ; in other 

 species elaters are wanting. 



In some species, the capsule splits, when ripe, longitudinally 

 into two or four valves ; in others, the dehiscence is transverse 

 and the upper part, called the operculum, comes off like a lid ; in a 

 few forms the dehiscence is irregular, and rarely there is none at 

 all, but the spores are set free by the decay of the capsular walls. 



