NOTES ON POTAMOGETONS. 373 



condition out of Europe that have not fruited. The way to settle 

 this point would be to transplant a specimen of what we here call 

 a hybrid, plant it in a hot country, and see the result. 



In his synonymy under this plant, he gives P. pumilus Wolfg. 

 This is an error; I have seen an original specimen, and it is 

 P. Claytonii Tnckermau. He also queries P. Nuttallii Cham, as 

 the same ; this is not so ; it is either (as I think) P. Oakesianus 

 Eobbins or, as Dr. Morong supposed, P. Clai/to7iii. The other 

 synonyms he gives it is possible to dispute at all points ; they are 

 "good species " to many botanists, to others not even varieties. 



I am doubtful whether his P. stenostachijs, t. 119, f. 1, is not 

 another variety or subspecies of the aggregate Jiuitans. The " small 

 red fruit" can, I think, be matched, but I have not seen his 

 specimens. 



Neither have I seen his P. sclerocarpus, figured on t. 120, f. 2. 

 With it he figures P. ijolygonus Cham., and the two look much 

 alike, except that sclerocarpus has floating leaves, which the other 

 is not known to possess. We do not seem to possess in Great 

 Britain either of Eiedel's numbers that he quotes for the two new 

 species. 



I have never been able to assure myself that Gardner's No. 2756 

 could possibly be referred to P. lucens L., as Dr. Schumann 

 supposes. Of course it comes under that species as an aggregate, 

 but its habit is different from any other lucens. Doubtless it may 

 be said that the tropical part of Brazil whence it comes may alter 

 its habit considerably by the highly heated water it grows in. 

 I believe now that I led Dr. Schumann into the error of supposing 

 that P. GaiuUchaudii Cham, was conspecific with lucens. I now 

 quite believe it to be the P. mucronatus of Presl in Rpim. Bot. (1849), 

 and the fruit of this and the peculiar conformation of the leaves are 

 so different from typical hicens that I cannot conjoin them together. 

 Dr. Morong, when describing P. Wrightii (believing it to be un- 

 described), says that the fruit is the most distinct he has seen. 

 P. Ulei Schumann {Ule, No. 1919), "Santa Catherina," he does 

 not figure, but compares it with P. ochreatus Eaoul of N. Zealand. 

 I do not think we have anything in our herbaria that can be placed 

 to his plant, unless it has been received quite recently. 



P. pusiLLUs L. With most of the names he places under this 

 I agree, but P. denticulatum Link, notwithstanding what Keichen- 

 bach says in his Icones, must go to P. tricholdes Cham, rather than 

 ■pusiUus. Dr. Schumann reduces P. tenuifolius Phil. ined. (= P. 

 Aschersonii mihi) to a var. of pusillus. If one considers the evolution 

 of the beak of this plant and pnsiUus (just as Dr. Schumann figures 

 those on t. 120, f. 1/r., fig. 2//-.), then they are distinct as sub- 

 species anyhow; but this will vary on the same spike. The specimens 

 are so scarce, and none too good, that it is difiicult to get enough 

 material to dissect a number of fruits. 



Dr. Schumann's P. pcctinatus is an aggregate species embracing 

 the five-leaved genuine form of the Linnean herbarium, to the stout 

 zosteraceus of Fries, and the Vaillantii of Koemer & Schultes. He 

 adduces P. trichoides as an analogous species, in which the fruit 



