ANGIOSPERMAE 



CLASS n. MONOCOTYLEDONES 



CVI, ORDER HYDROCHARIDEAE DC. 



Literature. — Ascherson u. Giirke, ' Hydrocharitaceae,' in Engler u. Prantl's 

 'D. nat. Pflanzenfam.,' II, i, pp. 244-5. 



Kerner's description ('Nat. Hist. PI.,' Eng. Ed. i, II, pp. 130-3) of the flower 

 mechanism of Vallisneria spiralis Z., V. altemifolia L., Enalus acoroides L., Hydrilla 

 verticillata L., Elodea canadensis Michx., and species of the genus Lagarosiphon, 

 has been given in Vol. I of this work, pp. 68-9. 



Flowers monoecious, dioecious, trioecious or hermaphrodite. Entomophilous 

 or hydrophilous. 



812. Hydrilla Rich. 



Flowers hydrophilous; monoecious. 



2599. H. verticillata Presl. (Ascherson u. Giirke, op. cit.) — The short-stalked 

 male flowers of this species are solitary. At the time for pollination they separate 

 from the submerged plant and float on the surface of the water. The female flowers 

 possess a calyx-tube elongated to a thread (which Ascherson describes as an ovary), 

 and three filiform stigmas, which are pollinated by the floating male flowers. 



813. Elodea Mich. 

 Flowers hydrophilous; trioecious. 



2600. E. canadensis Michx. (Ascherson u. Giirke, op. cit.) — It is a familiar 

 fact that only the female plant of this species has been imported into Europe, and 

 this propagates freely in a vegetative manner. In North America the plant is 

 trioecious and hydrophilous. As in Hydrilla verticillata the male flowers separate 

 from the plant and float on the surface of the water, where they reach fixed female 

 ones, of which the inferior ovary is prolonged into a thread, so that its purple stigmas 

 can be pollinated by the male flowers. 



814. Vallisneria L. 



Flowers hydrophilous ; dioecious. 



2601. V. spiralis L. (Delpino, ' Ult. oss.,' II.) — The submerged plants of this 

 South European species free their numerous male flowers, which are situated on short, 

 radical stalks, at the time for pollination, so that they rise to the surface of the 

 water. At the same time the female flowers unroll their spiral, filiform stalks, being 

 thus brought to the surface, where they are pollinated by the male flowers. After 

 pollination the flower-stalks once more roll up, bringing the flowers back to their 

 original position where the fruits are set. (C/I Vol. I, p. 69.) 



