CONIFERALES 63 



plasm and not pitted. The former cells are said to represent 

 an extension of the tracheid system, passing water from the 

 xylem to the mesophyll; and the latter to mediate between the 

 mesophyll and the phloem in the transfer of organized material 

 (Fig. 47). 



The single bundle which enters the leaf divides into two 

 strands in the narrow leaves, and the strands run parallel and 

 near together with a common bundle sheath. In broader leaves 



* 



FIG. 47. Pinus Laricio, cross section of a needle, x 70. 



the bundle divides into several more divergent strands. In no 

 case do the veins come near the surface, but run through the 

 middle tissue. 



THE ROOT 



In strong contrast with the Pteridophytes, the primary root 

 in Conifers persists as a tap root; while, according to De 

 Bary 27 , following Strasburger, 17 the differentiation of the 

 meristem at the apex is essentially different from that of 

 Angiosperms, as was indicated in connection with the Cycads. 

 The description given by De Bary is essentially as follows, 

 and the accompanying figure (Fig. 48) from the same source 

 will fully illustrate it: "A plerome cylinder with sharp 



