440 



BOTANY 



The Bryophyta and Pteridophyta have accordingly been classed 

 together as Embryophyta by ENGLER, and termed Embryophyta 



zoidiogama because the male cells 

 are developed as spermatozoids. 



The asexual generation or sporo- 

 phyte is represented by a plant 

 possessing a highly differentiated 

 internal structure, and externally 

 segmented into stem, leaves, and 

 roots. In the majority of Pterido- 

 phytes (Ferns, Equisetum), the fertil- 

 ised egg-cell, while still in the arche- 

 gonium, surrounds itself with a cell 

 wall and undergoes division, first into 

 two cells, by the formation of a 

 transverse or basal wall, and then 

 into octants by two walls at right 

 angles to each other and to the basal 

 wall. By the further division of 

 these eight cells a small mass of 

 tissue is formed, and from this are 

 developed the stem apex, the first leaf, the primary root, and an 



Jt 



FIG. 401. Transverse section of the rhizome 

 of Pteris aquilina. s, Concentric vascular 

 peripheral bundles ; I, sclerenchymatous 

 plates ; Ip, zone of sclerenchymatous.flbres; 

 JJ, cortex ; e, epidermis, (x 7.) 



FIG. 402. Transverse section of stem of Lycopodium cornea nntum. rp, Epidermis ; i-t, vi,pp, outer, 

 inner, and innermost parts of the primary cortex, surrounding the central cylinder formed 

 by the coalescence of concentric bundles; sc, scalariform trachcides ; s}>, annular and spiral 

 tracheides ; v, phloem, (x 26.) 



organ peculiar to the Pteridophytes, the so-called FOOT (Fig. 400 /). 

 The foot is a mass of tissue, by means of which the young embryo 



