EMBRYOLOGY OF EQUISETUM. 



743 



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

 completely enclosed in the tissue of the parent-plant. While the embryo itself 

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

 creases in 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. 425.-^4 male prothallus of Equisctunt 

 arvense, with the first antheridia a (after Hof- 

 meister, X 200). B—F- antlierozoids of Equisctum 

 Teimateia (after Schacht). 



Fig. 426 \'ertical section of the lobes of a 



vigorous female prothallus of Hquisetum at-vensc 

 (after Hofmeister). At aaa two barren and one 

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



FIG. 4=7.-Developn,ent of the embryo of H.,uisctum arvense (after Hofn.e.ster). -■' v>:rt.cal section of 

 archegoniim a with e.l.bryoyiX =00). B a free en.bryo further developed : Ö UK.p.ent «- --« i^-^^-J_ 

 the first shoot (X =00). C vertical section of a lobe of a prothallus// w.th a young i-/«»./;»«. «.its first root, 

 b b 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 ai^cal cell for the first root 

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



