274 



NOTES ON PONDWEEDS. 



translucent, immersed in the substance of the leaf, which is perfectly 

 smooth on both surfaces. These leaves are produced alike on 

 barren and flowering shoots, and are bright green, thick, and 

 remarkably brittle when fresh ; varying in shape from elcngate- 

 lanceolate to oblong or elliptical, but all are qradually narrowed into 



the petiole, even when they are slightly auricled or folded towards the 

 Use, in which case the lamina is shortly decurrent below the fold. 

 The convex petiole is from f to 1| in., the lamina from 3 to 5 in. long. 

 The stipules are large, 8-4 in. long, very rarely with a leaf 

 reduced to a phyllode on the hack, closely clasping the stem at first, 

 but afterwards becoming reflexed when a branchlet springs from 

 their axils, horny, hyaline, with two prominent, green, winged ribs 

 on the back and numerous slender green ribs on the sides, which 

 are connected by anastomosing veins ; horn-coloured, or the 

 lowest sometimes tinged with red like the base of the stem. They 

 are curiously persistent even when decayed, not splitting into fibres 

 like those of P. nutans. 



The flower-spike is subtended by opposite leaves ; before expan- 

 sion it is like that of P. decipiens; when in flower the sepals are 

 delicate bright green, and the spike closely resembles that of 

 F. Zitn. The immature fruit is S-keeled, with the central keel 



rather prominent. Mr. W. H. Beeby has sent me some detached 

 Iruits, found amongst some Surrey plants of this species recently 

 gathered by him, which are more advanced than any I have seen in 

 the .bens. These when fresh resembled half-grown fruit of P. 

 nutans, but were very slightly keeled on the back ; when dry they 

 became distinctly keeled. Although they very probably belong to 

 the plants amongst which they were found, the degree of uncer- 

 tainty winch attaches to them renders a more exact description 

 undesirable. 



When forsaken by the water P. ftuitaru produces subaerial 



le* 



I have 



leaves, and continues to grow until cut down by frost. 



JWy described this state of the plant in 'Journal of Botany' 



p i- •■ V? " 8 ° 7 ' ^" s land-form more nearly resembles that of 

 • f mt thau ai >y other species I have observed, but it seems not to 

 produce phyllode$, so usually found in land-forms of the lucens-gromp. 

 ihe autumnal state of P. fltutam is so unlike the early and 

 P- Meet states as to look like a distinct species. Specimens of this 

 sta e were first gathered in Surrey in 1886, by Messrs. W. H. Beeby 

 ana Arthur Bennett. Dr. Tiselius, to whom they were submitted, 

 nought they might belong to P. zosterafoUm ; while Mr. Beeby 

 cleverly suggested that they were probably a form of P. heterophils, 

 J™ wwwmaDj elongate lower leaves ; a guess only just short of 

 uie truth, for P.ftuitam is undoubtedly closely allied to the section 

 oi me genus to which />. heterophil! us belongs. The guesses (for 

 ™ey aid not claim to be more) of these two skilful botanists 

 wui grve S ome idea of the appearance of this autumnal state, so 

 unlike the usual form of the species seen in herbariums. The 

 prooiem ol the specific rank of this puzzling Surrey plant was 

 soivea in the autumn of 1887, when I gathered exactly similar 

 specimens from a plant of P. fluitans which I had watched from 



