ENDS AND CONNECTIONS OF THE BUNDLES. 



381 



namely elongated ; but they are on the average shorter and wider, and have terminal 

 surfaces, which are but little oblique, and may even be horizontal. As their distance 

 from the inner edge increases, their length rapidly diminishes, while their width 

 increases, so that in the outer part of the border they are not longer, and are often 

 even shorter than they are broad, being similar in form and size to the neighbouring 

 parenchymatous cells. 



These conditions appear in a special form in Podocarpus IVteyeriana, Thuja 

 gigantea, and in the Pines and Abies excelsa. In the two first-named the border is 

 very broad, it projects deeply into the middle of each half of the leaf in the form of a 

 flat wing. Its tracheides, with the exception of the innermost, are, with reference to 

 the diameter of the leaf, much broader than long, thus 'having their greatest diameter 

 directed towards the edge of the leaf; they form rows running towards the latter, 



Fig. 184.— Juniperus communis (225). Median vascul.ir bundle of the leaf. .?• xylem ; c isolated sclerenchymatnus 

 fibres at the outer border of the phloem; t border, consisting of tracheides with borderetl pits and cross beams. 

 The parenchymatous cells occurring near or between the latter are dotted in a granular manner. 



which are often interrupted, but are in contact with one another, and might be 

 termed a narrow-meshed net of uniseriate vascular bundle terminations. 



In the connate sheathing-base of the 

 fiat pair of leaves of Thuja gigantea, the 

 border of tracheides of each leaf is expanded 

 into a low wing, which runs to meet that of 

 the opposite leaf, and unites with it to form a 

 transverse girdle. 



In the Abietineae last-mentioned^, the 

 pair of vascular bundles lies in an approxi- 

 mately cylindrical central portion of the leaf, 

 which is free from chlorophyll, and is se- 

 parated from the surrounding chlorophyll- ,,.^ l^-':':^:^^ ^'^^^1:1,^'::^ 

 parenchyma by a parenchymatous sheath :^l::::^^^,!^l^Z::':^:{.f::^:::^t 



with somewhat stouter walls (cf. Fig. 185). ■^af.^con^ining the two vascular bundles. I-rom Sachs- 



' See Hartig, Naturgesch. d. forstl. Culturpflanzen. 



