344 



MALE CONES 



the transfusion tissue) are special peculiarities of the group. 

 The necessity for the reduction of transpiration may well be 

 connected with the relative inefficiency of the tracheids as water- 

 conducting elements. 1 The relation between the vascular system 

 of stem and leaf in Conifers is similar to that which obtains in 

 Flowering Plants (cf. p. 114). 



FIG. 199. Structure of the leaf of Pinus in transverse section. A, Diagram 

 of whole section. B, Small part of the superficial tissues, enlarged. 

 C, A few cells of the transfusion tissue, etc., from the central vascular 

 cylinder, greatly enlarged . D, About half the central vascular cylinder. 

 a., albuminous cells ; b., bordered pit on transfusidn cell ; Cu., cuticle ; 

 ep., epidermis ; h., hypoderm ; i., folds on walls of mesophyll-cells ; 

 ph., phloem ; r., resin-canal ; 5., bundle-sheath ; ScL, sclerenchyma ; 

 St., stomata ; tr., elements of transfusion tissue ; xy., xylem. 



The sporophylls of Conifers, like those of Cycads, are grouped 

 in cones (Fig. 200), the two kinds being most commonly found 

 on the same plant, though Taxus (Fig. 201), for instance, fur- 

 nishes an exception. The male cones, which often occur in 

 clusters (Fig. 200, on the right), are yellow oval structures of 

 diverse size, and frequently arise in the axils of the foliage- 

 (e.g. Taxus, Fig. 201, e ; Abies, Fig. 193, A) or scale-leaves 



1 Cf. F. and S., p. 114. 



