1907] CHRYSLER— POT AMOGETONACEAE 187 



EXPLANATION OF PLATES XIV-XVIII 



PLATE XIV ^ 



Diagrams to show the course of the leaf traces in the different genera. In 

 each diagram the upper part represents a transverse section through the node^^ 

 and the lower part a longitudinal section through a node and part of the inter- 

 node below it. The boundary of the central cylinder is indicated by broken 

 lines, the median leaf trace by a double line, and the lateral leaf traces by single 

 lines. In the vertical diagrams the median trace is represented for the sake of 

 clearness as if entering from one side. 



i 



Fig. 4. Potamogeton (most species). — Fig. 5. Potamogeton Nuttallii, — Fig. 6, 

 Zostcra marina, — Fig. 7. Phyllospadix Scouleri. — Fig. 8. Cymodocea manatorum. 



w 



— Fig. 9. Ruppia maritima. — Fig. 10. Zannichellia and Xaias. 



PLATE XV 



Fig. II. Potamageton natans. Transverse section a little above an upper 



node of the leafy shoot, showing the petiole, fused stipules, axillary bud, and 

 stem. X15. 



Fig. 12. Same. Longitudinal section through an upper node, showing the 

 swellings at the origin of leaf and branch bundles. X20. 



Fig. 13. Same. Part of fig. 11 more magnified; numerous cortical bundles 

 are visible. X20. 



Fig. 14. Same, Central cylinder of fig, ij more magnified. X4S. 



Fig. 15. Same. Transverse section through the central cylinder at a node 

 of the leafy shoot. X^S- 



Fig, 16. Same. Transverse section through in ternode of the creeping stem; 



cortical bundles are absent. X35. 



PLATE XVI 



Fig. 17. P. piilcher. Tran'sverse section through central cylinder of the 

 creeping stem at the origin of a branch. X20. 



Fig. 18. P. pedinatus. Transverse section through the leafy stem a short 

 distance above a node. X55. 



Fig. 19. P. pidcher. Transverse section through the leafy stem just above 

 a node, showing the absence of cortical strands characteristic of this species. 

 X20. 



Fig, 20. Same. Central cylinder of fig. ig enlarged, showing the separated 

 bundles. X70. 



Fig. 21. Same. Transverse section through an intemode of the creeping 

 stem, showing the tubular central cylinder. X20. 



Fig. 22, Same. 



80 



Fig, 2^. P. natans. 



PLATE XVII 



erse section 



axis, showing a ring of bundles. 'X35. 



