DIV. 1 



PTERIDOPHYTA 



511 



with spermatozoid mother cells, and enclosed by a wall formed of 

 two ring-shaped cells and a lid-cell. 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. 



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 



FIG. 476. Poly podium vuJgare. A, Young archegonium not yet open ; K', neck-canal-cell ; 

 K", ventral-canal-cell ; o, egg-cell ; B, mature archegonium, open. ( x 240. After STKASBURGER. 



prothallium, consists of a wall composed of a single layer of cells 

 made up of four cell rows (Fig. 476); it encloses the elongated neck- 

 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. 462. 



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

 budding or direct vegetative growth ; the sexual organs are not formed or they 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). 



OFFICIAL. Dryopteris (Aspidiuni) filix mas, provides FILIX 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, and also for stuffing cushions, etc. 



