342 



' LAW OF LOSS ' 



[CH. 



Phy iiodic Anatomy inFontedenacea 



"^b- ^'^-K h.b.o.b o.h .^L.^^?" 



PP' B. Pontederia 



px. p'K. xy PP- c 



"^ :^ ^Pontedena 



EicKhornia 



lib. Heteranthera renifomils 



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 ccr- 

 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 bra^nch. 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 [ni.b.). All the bundles 

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

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



[Arber, A. (191 8).] 



