ANATOMY OF MEGALODONTA BECKII 34 1 



in area and number of elements. (Fig. 13). Calcium oxalate 

 crystal aggregates are sometimes found. 



EMERSED LEAVES. 



The emersed leaves are oblong to lanceoplate sharply or even 

 laciniately toothed, and the intermediate ones between the aquatic 

 more or less cleft or lobed. In structure they are bifacial. A 

 surface view of the epidermis of the upper face is more regular 

 or rather less irregular in cell structure (Fig. 14). The stomata 

 are smaller than those of the lower face and orbicular whereas 

 below they are slightly larger and oval. (Fig. 15). The chloren- 

 chyma viewed from the lower face has many intercellular spaces 

 (Fig. 16). It changes in shape gradually as it passes inwards to 

 the two layers of palisade chlorenchyma. Ijjearer the midrib the 

 palisade as well as the chlorenchyma pass gradually into rounder 

 chlorophylless cells on both faces. This is augmented by two 

 lavers of thick walled cells (Collenchyma) on the lower face and 

 a wedge of similar stereome on the other face. Sectioned about 

 the middle of the leaf there is a large central collateral bundle 

 with several lateral ones in a semicircle (Figs. 17 and 18). In 

 the petiole or at the base of the leaf these are coalesced into one 

 Large semicircular collateral bundle. Opposite to the phloem 

 strand and immediately under the stereome on the lower face. 



The characteristic features of the plant are the very simple 

 wood bundles undergoing scarcely any secondary changes, as 

 also the simplicity and regularity of all the structures. The roots 

 are in the adult stage of the plant all adventitious and develop 

 chlorophyll regularly as far as the stele. The stomata of both faces 

 of the leaves are somewhat diderent and the extrastelar cells of 

 the aquatic foliage exclusive of the epidern'is have very character- 

 istic scalariform m.arkings. The aquatic foliage is as typically 

 centric in type as the aerial leaves are bifacial. 



EXPLANATION OF THE FIGUREvS. 



Fig. I. — Cross section of the young root of Megalodontu. Beckii. (a) 

 cortical intercellular spaces, (h) smaller spaces, (c) endodcrmis, (d) peri- 

 cycle, (/) phloem (leptome), (/) xylem (hadrome), {g) pith, (/?) latex tube. 



Fig. 2. Cross section of the epidermis (ep) and hypodermis (hy) 

 of an older root, (co) cortical chlorenchyma. 



Fig. 3. Structure of a latex tube in an older root showing the arrange- 

 ment of the secreting cells. 



