98 



BOTANY 



PART I 



inserted at this node. The two lateral strands of each leaf-trace (Fig. 115 b, c ; 

 e,f' } h, i; l,m; o,p; r, s] are also free through the internode, but at the node below 

 they curve inwards and become attached to the same lateral strands as the arms 



of the median bundle of the trace. 



The course of the bundles in the 

 Monocotyledons follows a wholly 

 different type (Fig. 116). The indi- 

 vidual bundles of the leaf-trace pene- 

 trate to different depths in the stem 

 and thus appear scattered on the cross- 

 section. This results from the prolonged 

 growth in thickness of the growing 

 point after the procambial strand of 



ale 



FIG. 115. Clematis viticella. End of a branch 

 which has been made transparent by the re- 

 moval of the superficial tissues and treatment 

 with caustic potash. The emerging strands 

 have been slightly displaced by gentle pressure. 

 The two uppermost pairs of young leaves (bl 1 , 

 bl 2 ) are still without leaf- traces, v, Apical cone. 

 (After NAGELI.) 



FIG. 116. Diagrammatic representation 

 of the course of the bundles in the Palm 

 type. Two-ranked leaves encircling the 

 seem are shown cut in their median 

 planes. The leaves (Aa, Bb, Cc) are 

 cut across close to the base ; the capital 

 letters indicate the median portion of 

 each. The stem is seen above in trans- 

 verse section. (After ROTHERT, adapted 

 from ROSTAFINSKI.) 



the first and median bundle of the leaf is laid down. As a result of this 

 the successively-formed procambial strands of the later bundles are placed less 

 deeply. This arrangement is especially well marked in the Palms (palm type), in 

 which each leaf-trace consists of the numerous bundles which pass into the stem 

 from the leaf -base which completely encircles the stem. The median bundle 

 penetrates to the centre of the stem, the lateral bundles, as the median line of the 



