,^2 AMERICAN MIDLAND NATURALIST 



I'ig. 4. Longitudinal section tlirough the central part of an older 

 root. (a) epidermis, (b) hypodermis, (c) cortical parenchyma with 

 chlorophyll, (d) intercellular space, (e) extrastelar fundamental tissue the 

 outer cells with chlorophyll, (/) endodermis, (g) pericycle, (h) secretion cells 

 with a latex tube between them, (/) phloem, (/) wood parenchyma between 

 the protoxylem and inner metaxylem. 



Fig. 5. Cross section of a secton of the stele of the rhizome, (sp) 

 cortical intercellular space, (co) cortex cells, (la) latex tube, (st) stereome 

 outside of the phloem of the fibrovascular bundle (mestome), {c'a) Cambium, 

 (pi) pith. 



Fig. 6. Cross section showing the arrangement of the bundles in 

 the stem of the same. The xylem is cndarch pentarch. 



Fig. 7. Cross section of the stem (floating, showing the arrangement 

 of the bundles. Figs. 6 and 7 diagramatic and magnified about 18 diameters.) 



Fig. 8. — Cross section of the floating equatic stem showing (e) epidermis 

 with cortex beneath in which are the latex tubes (la) and the large inter- 

 cellular spaces isp) farther in the stele with the collateral bundles and the 

 outwardly bulging pith (Medullary rays) (w), the central pith (pi), (xV) 

 the protoxylem and (xy^) the mataxylem. 



Fig. 9. Cross section of medium sized division of the aquatic leaf 

 a little above the middle, showing the outer layer of epidermis with chlor- 

 ophyll and the inner mesophyll also with chlorophyll. In the centre is the 

 single fibrovascular bundle with a few xylem and phloem elem.ents also 

 a latex tube. 



Fig. 10. One of the larger mesophyll cells of the above teased out to 

 show markings of the cell wall. 



Fig. I I . Single fibrovasular bundle of a larger division near the base 

 of petiole, ipli) phloem and (.V3') xylem. (ivp) wood parenchyma, and (me) 

 mesophyll. 



Fig. 12. View of the epidermis of the aquatic leaf divisions. 



Fig. 13. Cross section of the bundle of the aquatic leaf petiole with 

 bundle of (xy) xylem and (ph) phloem, (gl) latex tube, (cr) crystal aggregate 

 of calcium oxalate. 



Fig. 14. Epidermis of the upper face of the aerial leaf with stomata. 



Fig. 15. Epidermis of the lower face of the aerial leaf showing stomata. 



Fig. 16. View of the pneumatic tissue under the epidermis of the 

 lower face of the emcrsed leaf. 



P'ig. 17. Cross section of the middle part of an aerial leaf at the midrib 

 (ep) lower epidermis with collenchyma or thick angled cells within it, (c), (co) 

 fundamental tissue, (ph) phloem and (xy) xylem of the collateral bundles, 

 (pi) modified palisade chlorenchyma. 



Fig. 18. Cross section of an emersed leaf showing the arrangement 

 of (ep) the lower epidermis, (clil) pneumatic chlorenchyma, (pa) ])alisade 

 chlorenchyma. (st) stomata. 



Scale of all llu- drawings: one division equals 12.5 microns. 



