478 



BOTANY 



PART II 



the wall and the cells which give rise to the spermatogenous tissue. In the Mosses 

 (Musci), on the other hand, the antheridium develops by the segmentation of a 

 two-sided apical cell, which is delimited by two oblique walls in the uppermost 

 cell of a short row. Each of its segments is later divided into wall cells and an 

 internal cell which contributes to the development of the spermatogenous cells 

 (Fig. 435 A-F). 



The archegonia (Fig. 436) are short-stalked, flask-shaped organs in 

 which a venter and neck can be distinguished. The wall of the ventral 



portion encloses a large 

 central cell, which divides 

 shortly before maturity 

 ^4 to give rise to the egg- 



^y^ cell and the ventral- 



canal-cell. The latter if 

 situated at the base os 

 the neck, just below a 

 central row of neck- 

 canal-celfe, the number 

 of which is lower in 

 Liverworts (4-8) than in 

 Mosses (10-30). The 

 neck opens by the swell- 

 ing of the mucilaginous 

 contents of the upper- 

 most cells which rupture 

 the cuticle and often 

 become rolled back as 

 four lobes (Fig. 438 B) 

 ( 95 ). The canal-cells be- 

 come mucilaginous. Since 

 water is essential for the 

 process of fertilisation, 



FIG. 436. Marchantiapolymorpha. A, Young, B, mature arche- ^ nis on V takes place in 

 gonium ; C, fertilised archegonium, with dividing egg-cell, laild-f OmiS after Wetting 



k', Neck-canal-cell ; k", ventral-canal-cell ; o, egg-cell ; pr, 

 pseudo-perianth, (x 540. After STRA.SBURGER.) 



!, rain Or dew The 

 * , , 



movement of the sperma- 

 tozoids towards the archegonia, and down the neck-canal to the egg-cell 

 is directed by particular substances diffusing from the archegonium. 



The spermatozoids of Mosses are attracted by cane-sugar solution, those of the 

 Liverwort Marchantia also by proteid substances and by salts of potassium, rubi- 

 dium, and caesium ( 96 ) (cf. p. 331). 



The archegonium develops from a single superficial cell. In Liverworts this 

 divides into a lower cell, which gives rise to the stalk, and an upper cell ; the 

 latter is divided by three longitudinal walls into three outer cells surrounding a 

 central cell. The central cell is then divided by a transverse wall into a cap-cell 

 and a completely enclosed internal cell. The outer cells give rise to the wall of 



