LECT. VIII.] STRUCTURE OF HERBACEOUS ROOTS. 435 



perfected; at which time the short tubes are 

 emptied, and their sides gradually become ligne- 

 ous and opaque. 



The root of the Carrot, Daucus carota, re- 

 sembles that of the Burdock in general structure, 

 but the sap vessels are comparatively more nu- 

 merous, and the cellular rays more condensed. 

 The cells and short tubes are rather four-sided 

 than hexagonal; and there is no symmetrical ar- 

 rangement of the latter. The sap vessels are all 

 punctuated, even the smallest and most recently 

 formed, which militates against Kieser's opinion of 

 transformation. 



In the root of Hemlock, Conium maculatum, 

 the sap vessels are situated chiefly in the centre, 

 in fasciculi, interspersed with cellular matter, dis- 

 posed in narrow wedgelike masses, divided by 

 more condensed cellular matter, closely resem- 

 bling the divergent rays in the roots of trees. The 

 cortex is thick, and contains various fasciculi of 

 proper vessels, disposed at regular distances, so 

 as to form a kind of double circle. The sap vessels 

 are punctuated spirals. 



Such is the structure of these three biennial 

 roots. The diversity they display is sufficient to 

 demonstrate the variations in the position of the 

 parts, which occur in biennial herbaceous roots. 

 In all of them the proper vessels constitute the 

 greater part of the bulk of the root ; and appear 



FF2 



