KUNGL. SV. VET. AKADEMIBNS HANDLINGAR. BAND 55. N:0 5. 181 



P. coloratus Vahl x gramiiieus L. (P. Billupsii Fryer, Notes on Pondw. 

 in the Journ. of Bot., 1893, 353 p. p. (t. 338, non t. 337!), by Fryer held for 



scoriaceus X plantagineusn). 



The English specimens I have examined are by Fryer himself determined as 

 P. Billuj)sii and considered to be a combination of his P. coriaceus and coloratus, 

 which would mean P. gramineus X lucens X coloratus. Anything of P. lucens, how- 

 ever, cannot be discovered in the specimens here concerned, but, indeed, in the spe- 

 cimens figured in t. 337, which evidently are P. Zizii (i. e. gramineus X lucens) with 

 serrulated margins on the lower leaves and shorter petioles in the upper ones. In 

 the specimens figured on the plate 338 P. coloratus can easily be traced in the leaf- 

 texture, the lack of marginal one-celled teeth, and the petioles. P. gramineus on the 

 other hand appears in the apexes of the submersed leaves and in the sometimes long 

 petioles of the floating leaves, longer than the blades. The latter property often 

 occurs in P. gramineus, whereas it is never met with in P. Zizii, where the petioles 

 always are abbreviated by the influence of P. lucens. The feeble ligules are also 

 extraneous to a lucens-hsistavd ; they are intermediate between the above parents 

 suggested by us. Nor has the very weak, unbranched, and low-grown stem of 

 our specimens anything to do with, or reminding of P. lucens. The arrangement of 

 the vascular bundles of the stem are also intermediate. Cortical bast and vascular 

 bundles as in P. gramineus; endodermis of M-cells. 



Habitat: England, Cambs., Parsonware Drove, Eenwick, 92, Fryer (hb, Stock- 

 holm.), together with the hybrid P. Zizii, hb. Tiselius. P. Billupsii is also found 

 in Sweden, Gothland, in a rivulet emptying into Tenglingsmyr (hb. Hagstr.). — 



An interesting plant from East Africa, Island of Socotra, gathered by B. Bal- 

 four in 1880 (hb. Stockholm), has been described by Ar. Bennett. To complete 

 his description I am here going to add what I have noted down of this form: 



P. semicoloratus Ar. Benn., New Potamogetons, in Journ. Bot. 1910, 150. 

 — Folia submersa obtuse subcuspidata non cucuUata. Nervus lateralis intimus cum 

 nervo principali usque ad medium folii conjunctus. Petioli foliorum natantium 

 angusti, longi, laminas sequantes vel longiores. Laminae subcoriacese. Fructus (parum 

 evolutus) rostratus esse videtur in statu maturo. 



The submersed leaves are not rounded or cucullate at the apex but endowed 

 with a slight obtuse cusp. The lateral nerves follow the midrib up to the middle 

 of the leaf before bending out into the blade. Petioles of the floating leaves long, even 

 longer than the laminse, which in some leaves are subcoriaceous. Unfortunately the 

 specimens have no ripe fruit and no young pistils. In the stem-anatomy the form 

 deviates by an endodermis of typical 0-cells, and, for the rest, approaches very much 

 to the species of the Amplifolius-grou]), with which it also has the leaf-apex in com- 

 mon, and it is therefore possible, or even probable, that the species, when the pistils 

 and fruits have been studied, must be referred to this group. Till then it should be 

 considered as a connective link between the Colorati and the Amplifolii. 



