﻿same tendency, more easily seen than reduced to description on 

 paper, such as the colouring of the upper surface of the leaves, and 

 the look of the twigs and of the small repens-like leaves at the base of 

 the twigs ; the value of these comes out on comparison with S. her- 

 bacea x Mi/rsinites and another rather similar hybrid, Arbuscula x 

 herbacea, at various stages of growth, and has been taken into 

 consideration in determining this willow. 



NOTES ON POTAMOGETONS. 



By Arthur Bennett, F.L.S. 

 (Continued from Journ. Bot. 1893, p. 297.) 



Potamogeton helodes Dumortier, Florida Bdgica, p. 163 (1827). 

 When noticing the mode of treating the genus Potamogeton by Dr. 

 Richter in his PL Europe® (Journ. Bot. 1891, p. 75), where he 

 refers the above plant to a var. of ru/escens Schrad., I made no 

 remark on this; as, although I was aware that many authors 

 referred it to plantagineus Du Croz (especially M. Crepin in his 

 Man. Fl. de Beige), still I had never seen an authentic specimen, 

 and thought that Dr. Richter might have some special knowledge 

 of the plant. By the kindness of M. Crepin, I now possess an 

 authentic specimen of Dumortier's plant ; the plant is undoubtedly 

 a small form of P. color atm Hornm. = P. plantagineus Du Croz. 



P. mucronatus Schrad. (Journ. Bot. 1891, 150). I think the 

 difficulty respecting this plant can now be cleared up satisfactorily. 

 By the kindness of Dr. Schroter, of Zurich, I have had a series of 

 Potamogetons from various herbaria, to look over at my leisure. 

 Among them, in tbe collection of Dr. Leiner, I find a specimen of 

 P. Friesii Rupr., with the following label:— "Aus F. A. Frolich's 

 Herbar. Potamogeton compressus L. ; Schrad.' in litt. L. circa 

 Waltingen NeobovinsB in fluvis Wernif, Jul. 1809, mihi Schrader." 

 This seems to me to dispose of Schrader's claim to the name 

 mucronatus as applied to P. Friesii Bupr., and to point to Steudel's 

 reference as the true one; i.e., "P. lucens mucronatw." It may of 

 course be said— Did Schrader change his opinion as to the Linnean 

 species between 1809 and 1844, the date of the supposed mucronatus 

 of Beichenbach ? In Reichenbach's herbarium there was a sheet 

 of "P. compressus L." (i. e., P. Friesii Rupr.), but nothing is noted 

 of mucronatus as a synonym, or otherwise. The question is— Where 

 did Steudel get his information ? As yet I have come across nothing 

 in reference to mucronatus, prior to Steudel and Reichenbach ; yet 

 one would think there must be some record somewhere. 



Among a series of specimens of Potamogetons sent me by the 

 late M. Maximowicz are specimens of a variety of pectinatus that 

 seems deserving of a name. 



P. pectinatus L., var. mongolicus mihi. Mongolia occidentalis. 

 Terra Ordos, 1871, leg. Prezewalski ; herb. hort. Petrop. — Plant 

 drying a bright grass-green, with pale orange-brown stems and 



