EMBRYOLOGY OF EQUISETVM. 743 



now invested with a new cellulose wall, and the embryo produced from it are thus 

 completely enclosed in the tissue of the parent-pla^t. While the embryo itself 

 slowly grows up, with accompanying cell-divisions, the tissue investing it also in- 

 creases m volume, and cell-divisions result in it. The manner in which, not only 

 in the case of the Equisetaceae but also in the Ferns, the growing oospore (or 



Fig. 435. — v/ male prothallus of Equisehtm 

 arvense, with the first antheridia a (after Hof- 

 meister, X 200). B—E antherozoids of Bquisetum 

 Telmateia (after Schacht). 



Fig. 426.— Vertical section of the lobes of a 

 vigorous female prothallus of Eqitisetum arvettse 

 (after Hofmeister). At a aa two barren and one 

 fertilised archegonium; h root-hairs (x about 60). 



Fig. 427. — Development of the embryo of Equisetttvt arvense (after Hofmeister), j4 vertical section of 

 archegonium a with embryo/ {x 200). S a free embryo further developed: b incipient first leaves ; s apex of 

 the first shoot (x 200). C vertical section of a lobe of a prothallus >/ with a young .EyKtr^ft^wz; wits first root; 

 ^ d its leaf-sheaths (x 10). 



what is the same thing, the young embryo) first breaks up into so-called octants 

 by means of three walls standing at right angles to one another, which then 

 become further divided up by means of anticlinal and periclinal cell-walls, and 

 how in this way there arises at last a tetrahedral apical cell for the first root 

 and a similar one for the young shoots, and how the first inception of the leaf 



