58 



BOTANY AND PHARMACOGNOSY. 



gives rise to both kinds of organs unless stunted in its growth, 

 when it produces antheridia only. 



The antheridia either develop upon or are sunk in the tissues 

 of the prothallus. The archegonia (Fig. 34) are not flask-shaped 

 as in the Bryophytes. The venter containing the oosphere or egg-cell 

 (Fig. 34, e) is embedded in the thallus, the structure being sur- 

 mounted by a few-celled neck (Fig. 34, h). The inner cells of 

 the neck are known as canal cells (Fig. 34, k) and these at the 

 time of ripening of the egg swell and exit through the opening of 



>f /i 



Fig. 34. A, B, development of archegonia of a fern {Pteris) showing the neck (h), 

 the neck-canal cell (k) and oosphere (e). — ^After Strasburger. 



C, development of antheridium in the Venus-hair fern {Adiantum Capillus -Veneris): 

 prothallus (p), antheridium (a), sperm (s), sperm mother cell with starch grains (b); I, 

 immature state of antheridium, II, sperms developed, and III, discharge of sperm mother 

 cells and escape of coiled and pluriciliate sperms. — After Sachs. 



the archegonium, through which then the sperms enter, one of 

 which unites with the egg, thus effecting fertilization. The fer- 

 tilized egg or oospore takes on a cellulose membrane. 



The oospore which is held in the venter of the archegonium is 

 not a resting spore but germinates immediately and early differen- 

 tiates into the several organs (Fig. 35) . These arise independently 

 and include a stem-bud (Fig. 35, s) ; a first leaf or cotyledon 

 (Fig. 35, b) so called because it does not arise out of the stem as 

 the later leaves do; a first or primary root (Fig. 35, iv) ; and 

 a foot or haustorial organ (Fig. 35, /) whereby it obtains nutri- 



