344 



VASCULAR CRYPTOGAMS. 



divisions taking place. The substance of this Ca?ial-cell, as it is termed, is finally 

 completely converted into mucilage, swells and forces the apical cells of the neck 

 apart, escapes, and remains collected before the opening of the neck. The anthero- 

 zoids are retained by this mucilage and collect in large numbers before the archego- 

 nium ; a number force themselves into the canal of the neck, often finally stopping 

 it up ; a few reach the oosphere, force themselves into and disappear in it. The 

 entrance takes place at a lighter spot of the oosphere facing the neck, which is 

 termed the Receptive Spot ^ (compare the oogonia of Algae). After fertilisation the 

 neck closes. 



The Asexual Generatmi or Fern (as it is popularly termed) is developed 

 from the oospore or fertilised oosphere of the archegonium. At first the sur- 



FlG. 255.— Archegonia oi Adiantian Capillns- Veneris ( X 800) ; A, B, C, E in longitudinal optical section ; D in 

 transverse optical section ; A,B,C before, E after fertilisation ; h neck of the archegonium, st mass of mucilage, 

 e oosphere ; E, e the two-celled embryo (observed after lying one day in glycerine). 



rounding tissue of the prothallium keeps pace with the increase of the oospore, so 

 that this latter remains for some time enclosed in a protuberance springing from 

 the under surface, until the first leaf and root break through. The first processes 

 of division of the oospore are, as Hofmeister has shown in the case of Pieris aqidlina 

 and Aspidium Filix-mas, not entirely alike in diff'erent species. It is certain that 

 the first division-wall of the oospore is transverse to the longitudinal axis of the 

 prothallium, and inclined to it obliquely; as shown in Fig. 255, E, its inclination 

 is the same as that of the neck of the archegonium. It is also certain that each 



* Strasburger states that the act of fertilisation may be observed especially clearly in Cera- 

 topteris ; the forcible entrance of the antherozoids as far as the oosphere had previously been seen 

 by Hofmeister. 



