C-1 ENGLISH BOTANY. 



British Potamogetons in tlie Kew Herbarium, I did not perceive any 

 plant to Avliich tliis name was applicable. 



It may be knoAMi by its having the large fruit of P. natans, and the 

 leaves similar to those of the deep water forms of P. polygonifolius. 

 The nearest approach we have to it is the plant called P. sparganiifo- 

 lius by Professor Babington ; but that has always a bi'anched stem, 

 while P. fluitans has a simple one, like that of P. natans. 



P. GRACILIS. Fries. 



At one time Professor Babington was inclined to believe that a 

 plant gathered by Professor Olhver, near Dunstanburg, Northumber- 

 land, might prove to be this species ; but in the fifth and sixth editions 

 of the " Manual " he says it seems to be P. pusillus. 



ORDER LXXVIIL— ALISMACE^. 



Marsh or aquatic perennial herbs, or very rarely annuals, with a 

 creeping or cormose I'ootstock. Leaf-bearing stem generally unde- 

 veloped. Leaves commonly all radical, sheathing at the base, simple, 

 linear, or with an enlarged lamina which is sometimes cordate oi' 

 sagittate at the base and with parallel or cancellate venation. Stipules 

 none or nearly wholly adnate. Flowers perfect (rarely unisexual and 

 monoecious) on a leafless radical scape, ax'ranged in a panicle, raceme, 

 or umbel — rarely in a raceme at the extremity of a leafy stem. 

 Perianth regular, of 4 or 6 leaves; in the latter case the 3 outer ones 

 often smaller and herbaceous, the 3 inner larger and petaloid, some- 

 times all the 6 petaloid, occasionally all the 6 subherbaceous. Stamens 

 G to 9, or numerous. Ovary superior, free from the calyx, of 3, 6, or 

 numerous carpels, which are either distinct fi'om the first or separate 

 iiito cocca or follicles when the fruit is ripe, rarely the carpels are 

 reduced to one ; ovules 1 or 2 (rarely more) in each carpel ; styles 

 commonly short or almost absent; stigmas simple, more rarely plumose. 

 Fruit of dry cai*pels or cocca. Seeds solitary, 2 or rarely many in 

 each carpel, with a coriaceous testa, destitute of albumen; radicle 

 pointing towards the hilum. 



Sub-Ordee L— JUNCAGINACEJi:. 



Perianth with the segments all similar, herbaceous or somewhat 

 coloured. Stamens G or 7 ; anthers extrorse. Seeds 1 or 2 in each 

 cell of the ovary ; embiyo straight. 



