THE LEAF 249 
B. CoNvERGENT.—This type is mostly seen in monocotyle- 
dons. In Phormium tenax or New Zealand Flax the base of the 
blade is sheathing; it then converges and opens out above. In 
the various species of Iris the petiole is sheathing, the sides of the 
upper part being fused and functioning as a lamina. 
é. 
Af 
a e\ sé rs 
asserere 
Fic. 167.—Transverse section through portion of dorsiventral leaf blade of 
horehound (Marrubium vulgare). Upper epidermis devoid of stomata (up. ¢p.); 
lower epidermis which possesses stomata (/. ef.); palisade parenchyma (pal.); 
spongy parenchyma (sp. p.); xylem (x) and phloem (fh) regions of fibrovascular 
’ tissue of stronger vein; long-pointed non-glandular trichome (f); branched tri- 
chomes (ft!, ft2, ft); several types of glandular trichomes (gt', gt?, gt*, gt*). 
C. Centric.—This type of lamina is semi-centric to centric 
in shape. It is nearly always associated with Xerophytes. 
Centric laminz are produced gradually by an encroachment of 
the under on the upper surface, and the swelling of the whole. 
There are two kinds of centric laminz, the succulent-centric and 
the xerophytic centric. 
Fl 
