SUPPOSED HYBRIDITY IN POTAMOGETON. 177 



usually barren do, however, occasionally bear fruit. By the kind- 

 ness of Messrs. Bennett and Beeby, I possess fruit of " P. fluitans" 

 from four different continental localities ; these fruits seem to fall 

 under two forms, one of which the accompanying foliage shows to 

 be the form I regard as a distinct species, the other may be fruit of 

 the plant of Both, but foliage is wanting to prove this. All I can 

 at present claim, with any degree of certainty, is that P. fluitans of 

 the Fens is a hybrid between P. natans and P. lucens. It never 

 occurs but in single plants, and in localities so far apart as to 

 render it extremely improbable that fragments of living plants 

 sufficiently large to grow can have been carried by any natural 

 means. 



In my previous note on P. decipiens * I gave my reasons for con- 

 sidering that plant a hybrid, reasons I need not here repeat ; but 

 will mention one fact which suggests that P. decipiens in some 

 forms may possess pollen which is partly, though imperfectly, 

 fertile. Mr. H. Bromwich tells me that the form which he sent to 

 the Exchange Club as " P. decipiens, v. afline," seems to be as 

 fertile as any other Potamogeton. It certainly does seem so up to a 

 certain point. The fruit- spike swells its drupelets till about one 

 half grown, then they shrivel and remain dead on the spike (in our 

 Fen-land decipiens the drupelets usually rot quite away). 



This looks like a first effort in the direction of fertile pollen. I 

 do not think the stimulus that causes the swelling of the drupelets 

 to be foreign pollen from other species of Potamogeton, because the 

 spikes seem to swell regularly, not a single drupelet here and there. 

 Mr. Bromwich informs me the plant grows apart from other forms. 



That certain plants of Potamogeton which are not hybrids may 

 remain barren for many years, even under apparently favourable 

 conditions, is a fact I have already ascertained. And I think it 

 is fairly well known that such supposed hybrids as P. lanceolatus 

 of Smith, and P. varians of Morong, do rarely become fertile under 

 favourable conditions. Hence I am not unhopeful that many 

 of our hybrid Potamogetons may ultimately progress to more or less 

 perfect fertility. To keep this note within reasonable limits I can 

 mention only one other instance of supposed hybridity between dis- 

 tinct species of Potamogeton. In the summer of 1889, my nephew, 

 Mr. 0. B. Billups, sent me a remarkable form from the Biver Dee, 

 above Chester, under the name of " P. crispus." I at once referred 

 this plant to P. perfoliatus, a decision which received support from 

 other botanists ; but Mr. Billups, a very acute naturalist, was 

 unable to concur, and pointed out that the stem was compressed 

 like that of P. crispus, and that in habit the plant resembled 

 that species rather than perfoliatus. I planted several roots, and as 

 the plant grew it produced young shoots from the axils of the 

 leaves on the main stem, so like those of P. crispus as to require 



_ * My friend Mr. Beeby, who has often been helpful to me in my studies in 

 this genus, sends me the following correction on that note. " I do not find 

 1 empty ' anthers on your Fen-plant. As in nitens, they are simply unopened ; 

 and, as in that plant, they contain plenty of pollen— of a sort."— W. H. B. in litt., 

 May 10th, 1890. 



Journal of Botany. — Vol. 28. [June, 1890.] n 



