96 cabombacejE. 



Herb growing in ponds and pools, sending up, from a 

 fleshy prostrate rhizoma, long and forking stems bearing 

 above alternate oval and entire centrally peltate leaves, invo- 

 lute in vernation, brought by the elongation of the petioles 

 to the surface of the water, on which they float. Peduncles 

 axillary, equally elongated, bringing the solitary dull purple 

 flower to the surface, where it expands only in anthesis. 

 The stalks and other submersed parts are covered, especially 

 when young, with a thick coating of transparent jelly. 



Etymology. Brasenia is unexplained ; perhaps it was designed to com-* 

 memorate some obscure German botanist. Hydropeltis, which, being un- 

 fortunately the later name, must give precedence to that imposed by Schre- 

 ber, is the Greek equivalent of Water-shield. 



Geographical Distribution. The single species is abundant through- 

 out the United States and Upper Canada. It is most remarkable that what 

 appears to be the same species is also a native of Eastern New Holland, 

 where it was long ago detected by Mr. Brown ! 



Note. The jelly by which the stalks, &c, are thickly coated, I find to 

 arise from the rapid formation and rupturing of successive epithelial cells, 

 in the same way that mucilage is formed on the surface of animal mucous 

 membranes. The rhizoma of Brasenia contains oblong and transversely an- 

 nulated starch-grains of unusual size, the larger being 6 ^ 3 of an inch in length. 



PLATE 39. Brasenia peltata, Pursh; — of the natural size. 



1. Diagram of the sepals and petals (in the bud each set is imbricated). 



2. Vertical section of a flower-bud, enlarged. 



3. A magnified anther, seen obliquely from the outside. 



4. The same ; inside view, showing the slightly introrse dehiscence. 



5. A magnified pistil, seen laterally; and 6, posteriorly. 



7. Same, the ovary divided vertically, showing the dorsally inserted ovules ! 



8. An ovule, more magnified. 



9. Fruit, with the persistent perianth ; of the natural size. 



10. A ripe carpel, enlarged. 



11. Vertical section of the same, and of the ripe seed and embryo in its sac. 



12. Vertical section of the hilar end of the seed (much more magnified) 



made at right angles to that in fig. 11, parallel to the cotyledons, 

 one of which is cut away, and through the included 2-lobed plumule. 



13. Similar section, cutting the cotyledons at right angles to fig. 12; or 



same as fig. 11, reversed and more magnified. 

 11. Embryo, magnified ; the cotyledons opened, showing the plumule. 



