342 



' LAW OF LOSS ' 



[CH. 



Phyllodic Anatomy inPontederiacea? 

 ^y-'^-X^Jvb.o.b _ob__ n - b 



$ c/ 9 3 c $ QJ < o O _j_^ 



PP-sTPontederia mc 



p.p. 



f x 



n.b 



xy P : P- r 



-^Pontederia 



lib. HeterantKera reniforrrus 



HeterantKera zosteraefoUa 



m.b. 



FIG. 170. Leaf anatomy of Pontederiaceae. A, Eichhornia speciosa, Kunth, T.S. 

 lateral vein of 'lamina.' One small normal bundle (n.b.). One larger inverted 

 bundle (i.b.) higher in leaf is giving off a branch, also inverted. B, Pontederia coy- 

 data, L., half T.S. lamina near apex. All bundles inverted (i.b.) or oblique (o.b.) 

 except the median bundle (m.b.) and the three bundles n.b., n.b/, and n.b.". Fibres 

 (/) at margin; h.b. horizontal branch. C, Pontederia cordata, L., the part of the 

 T.S. shown in B which is included between the dotted arrows. One normal bundle 

 (n.b.) and two inverted bundles (i.b.), one with an inverted branch, m.c. = cells 

 containing a secretion, probably myriophyllin. D, Pontederia cordata, L., T.S. 

 petiole near its upper end, outlines of lacunae dotted. E, Heteranthera reniformis, 

 Ruiz, and Pav., part of T.S. of lamina, including midrib (m.b.). All the bundles 

 shown are inverted, except the midrib and main lateral. F, Heteranthera zoster ae- 

 folia, Mart., T.S. part of ribbon-leaf to show one normal and one inverted bundle 



[Arber, A. (1918).] 



