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NOTES ON PONDWEEDS. 

 By Alfred Fryer. 



Potamogeton crispus Li. — Eootstock terete, slender, creeping, 

 shalloAv-rooting ; stem compressed, obscurely quadrangular, guttered 

 on the flattened sides, rounded on the edges ; simple below, 

 branched above, and with short branchlets springing from the axil 

 of each leaf on the main stem. Leaves all similar, strap-shaped, 

 oblong, alternate, or sometimes opposite at the base of the branches 

 and in the upper part of the stem, rounded and semi-amplexicaul, 

 or slightly narrowed and sessile at the base ; strongly undulated, 

 crisped, serrulate, blunt, or narrowed towards the apex, without a 

 distinct mucro, flat and very finely serrulate on young submerged 

 growths ; with three prominent ribs, upper with two fainter ribs 

 near the margin connected by distant oblique veins ; brownish 

 green, tinged with red or purple or bright green, translucent, 

 shining, somewhat horny. Stipules small, very short, lacerated at 

 the apex, scarious, not persistent. Peduncles slightly curved, 

 springing from the forks of the branches, or lateral, rarely sub- 

 tended by opposite leaves, compressed like the stem, but not channelled 

 except in the slightly tapering upper part ; as long as or longer 

 than the subtending foliage. Spike short, few-flowered. Drupelets 

 (fresh) acuminate, with a long beak equalling or exceeding the nut ; 

 central, keel slightly winged and crested, with a conspicuous fleshy tooth 

 at the base almost parallel with the axis of the fruit, lateral ridges 

 obscure, blunt. Whole plant submerged except the spikes, which 

 are sustained for some time above the water even when in fruit. 



P. crispus is easily distinguished from all hitherto described 

 British pondweeds by its compressed stem, and by its remarkably long- 

 beaked fleshy fruit ; also, in the ordinary state, by its strongly undu- 

 lated crisped leaves. It is rarely, however, that the leaves are so con- 

 spicuously curled as in the specimen represented in 'English Botany ' 

 (ed. 3, pi. 1413) ; I have only once collected this extreme state. 



The plant begins to grow in late autumn, and continues growing 

 throughout the winter ; the young shoots, especially on the deeply 

 submerged barren branches, have flat and narrow leaves, which 

 have much the appearance of those of P. nbtusij'olius or of P. Friesii, 

 but may be known from those of all the species of " graminifolii " by 

 their finely serrulate but not flattened margins, and the branches by 

 their compressed stems. Authors generally consider that Hudson's 

 P. serratus (P. crispus var. serratus Lond. Cat. ed. 8) was founded 

 on this young state of P. crispus ; perhaps, however, it would be 

 better to restrict the name of P. serratus to a small flat-leaved form 

 of the species which is distinguished by its finely serrulate flat, 

 narrow, strap-shaped leaves even when the plant is in fruit. 

 Possibly this form may be a true variety of crispus ; but, as far as I 

 have been able to observe it in the Fens, where in some districts it 

 is common, it is more probably a state induced by local conditions. 

 It is usually found in ditches crowded with vegetation, and when 

 shoots from the same rootstock are able to struggle into an un- 



Jourxal of Botany. — Vol. 28. [August. 181)0.] y 



