344 XXV. REPRODUCTION OF THE BRYOPHYTA. 



The penetration of the spermatozoids into the neck-canal can 

 also be easily observed. For this purpose, instead of pure water, 

 we add to the preparation a drop which has previously lain on a 

 male receptacle. The spermatozoids quickly collect in the slime 

 expelled from an archegonium ; we see them enter the neck, 

 where they become invisible. A substance (which in the closely- 

 allied mosses is cane-sugar) is given off from the archegonium, 

 which acts as a chemical stimulus, and determines their direction 

 of movement. Thus they get into the slime given off from the 

 archegonium, in which they slowly move in the direction of the 

 opening of the neck. It is interesting to prove that in an un- 

 fertilised archegonium the neck does not close, and under such 

 conditions the archegonium slowly decomposes. If, on the other 

 hand, water containing spermatozoids is added to the preparation, 

 and the oosphere becomes fertilised, the neck closes, even after 

 a few hours, contracting progressively from above downwards. 

 Keep the preparation, and after twenty-four hours the presence 

 of a cellulose membrane around the fertilised oospore is easy to 

 recognise. In the course of the next few days the thickness of 

 this cellulose wall increases. 



Structure of the Sporogonium. The fertilised archegonia, which 

 we may find upon the longitudinal sections, show a shrivelled and 

 brown neck, while the oospore has divided (Fig. 124, C). Around 

 the base of the archegonium, from its foot, a cup-shaped sheath, 

 the so-called perianth ium (perigynium) (pr) begins to develop. 

 This soon encloses the entire swollen archegonium. Upon longi- 

 tudinal sections of receptacles which have already spread out 

 their radiating ribs, we see the bright green, swollen archegonia, 

 with base broadened to correspond, situated upon the surface of 

 the receptacle, and crowned by the remnant of the neck. From 

 the oospore gradually proceeds the sporogonium, which we see 

 in longitudinal sections, prepared from still older receptacles. 

 The sporogone consists of a shortly-stalked, oval, yellowish-green 

 capsule. The wall of this capsule is unilamellar ; if we spread it 

 out with needles, and examine it with stronger magnification, the 

 characteristic thickening rings in the otherwise thin-walled cells 

 will appear. The yellow-walled spores are finely punctate. 

 Between them lie narrow, long cells, tapering at both ends, and 

 distinguished each by two brown spiral bands on its wall ; these 

 are the elaters, The interior of the capsule is entirely filled with 

 spores and elaters. In capsules already opened (dehisced), we 



