264. 



DISTRIBUTION OF VEINS. 



[BOOK i. 



The midrib (fig. 56. 7) sends forth alternately, right and 

 left along its whole length, "ramifications of less dimensions 



fig. 56. 



than itself, but more nearly approaching it than any other 

 veins : these may be called primary veins (fig. 56. 3). They 

 diverge from the midrib at various angles, and pass to the 

 margin of the leaf, curving towards the apex in their course, 

 and finally, at some distance within the margin, forming an 

 anastomosis with the back of the primary vein, which lies 

 next them. That part of the primary vein which is between 

 the anastomosis thus described, having a curved direction, 

 may be called the curved vein. Between this latter and the 

 margin, other veins, proceeding from the curved veins, with 

 the same curved direction, and of the same magnitude, 

 occasionally intervene: they may be distinguished by the 

 name of external veins (fig. '56. 1). The margin itself and 

 these last are connected by a fine net-work of minute veins, 

 which I would distinguish by the name of marginal veinlets. 

 From the midrib are generally produced, at right angles with 

 it, and alternate with the primary veins, smaller veins; which 

 may not improperly be named costal veins (fig. 56. 5). The 

 primary veins are themselves connected by fine veins, which 

 anastomose in the area between them; these veins, when they 

 immediately leave the primary veins, I would call proper 

 veinlets (venula propria) (fig. 56. 4); and where they anasto- 

 mose, common veinlets (ven. communes) . The area of paren- 

 chyma, lying between two or more veins or veinlets, I name 

 with the old botanists intervenium. 



