450 



BOTANY 



of two ring-shaped cells (A, 1, 2) and a lid-cell (3). The spermatozoid mother-cells 

 are produced by the division of the central cell. They are discharged from the 

 antheridium by the pressure exerted by the swollen ring-cells, and the consequent 

 rupturing of the lid-cell. Each mother-cell thus ejected liberates a spirally coiled 

 spermatozoid. The anterior extremity of the spermatozoid is beset with numerous 

 cilia, while attached to its posterior end is a small vesicle which contains a number 

 of granules, and represents the unused remnant of the contents of the mother- 

 cell (Fig. 411 D, C; Fig. 98 ). 



The archegonia arise from the many-layered median portion of older prothallia. 

 They are developed from a single superficial cell, and consist of a ventral portion, 

 embedded in the prothallium, and a neck portion. The neck, which projects 

 above the surface of the prothallium, consists of a wall composed of a single layer 

 of cells made up of four cell rows (Fig. 412 A. B) ; it encloses the elongated neck- 



Fi<;. 412. 7'oZt/;>(/iiu vtilyan. -I, Younn iuvhi-pmiuin not vet <>]><MI ; A", nrck-cunal-crll ; 

 K", ventral canal-cell ; o, egn-cell ; B, mature arche^onium, open, (x '240.) 



canal-cell. The ventral portion contains the large egg-cell and the ventral-canal- 

 cell immediately above it. As the archegonium matures, the canal-cells become 

 disorganised, and fill the canal with a strongly refractive mucilaginous substance. 

 This swells on the admission of water, and, rupturing the neck at the apex, is 

 discharged from the archegonium, which is now ready for fertilisation. The 

 development of the embryo is represented in Fig. 400. 



In certain ferns the sporophyte may originate on the prothallus by a process of 

 budding or direct vegetative growth ; the sexual organs are not formed or take 

 no part in the production of the plant (apogamy). Conversely the prothallus may 

 arise directly, without the intervention of spores, from the tissues of the leaf 

 (apospory) ( ns ). 



OFFICIAL. Aspidium filix mas, Fiux MAS. 



The long silky brown hairs from the base of the leaf-stalks of various Tree- 

 Ferns, especially Cibotium Barometz, and other species of this genus, in the East 

 Indies and the Pacific Islands, are used as a styptic (Penawar, Djambi, Pulu). 



Order 2. Hydropterideae (Water- Ferns) 



The Water-Ferns include only a few genera, which are more or less aquatic in 

 habit, growing either in water or marshy places. They are all heterosporous. 



