376 THE JOURNAL OF BOTANY 



signs of any peduncles in my specimens, and looking to the great 

 difference in width of leaves assumed by some of the graminifolius 

 section I am not convinced that this is not a remarkable narrow- 

 leaved form of zosterifolius. Mr. Baagoe also sent a form of 

 zosterifolius named angustissimus from Vanning in Jyllandia 

 (1899). In this the leaves are even narrower than the last ; but the 

 whole habit is different, and so far as the immature spikes show, 

 it is rightly referred to zosterifolius. The stipules are quite free, 

 while in the last they are closely appressed to the stems. 



Another plant sent by Mr. Baagoe as crispus x rufescens I 

 cannot separate from rufescens (alpinus), having gathered just 

 such specimens among the many alpinus that I have collected. 



P. mascarensis Cham, in Linnaea, ii. 228 (1827). 



P. natans L. b. mascarensis Kunth, Enum. iii. 128 (1841). 



This species (?) seems to be extinct, like so many of the 

 Mascarene birds, as I cannot find it has been collected of late 

 years. Beyond the specimen in the Berlin Herbarium, I know of 

 only two others, one in the Paris Herbarium, and one in Delessert 

 Herbarium (labelled "P. natans L. Dans la riviere de Begiout, 

 Oct. 1832. Bove."). That at Berlin came from Kunth, who had 

 it from the Paris Herbarium in 1820. 



Dr. Johnstone, who resided on the Island of Mauritius, had no 

 such plant among the Potamogetons he kindly sent me. 



P. Eobbinsii Oakes in Hovey's Mag. vii. 180 (1841). On 

 fruiting specimens this species produces small spathulate leaves, 

 2 cm. long x 3 mm. wide ; these occur at the base of the peduncles, 

 similar in character to those on P. panormitanus Bivoni, only of 

 thicker texture. 



So far as I have seen these are not noticed in any North 

 American Flora, and Mr. Hill's plate (Bot. Gaz. xxv. 148 (1898), 

 t. 15) does not show them, although the very rare fruits, which 

 are winged on the central carina, are there well represented. I 

 do not find any of these leaves on my specimens of P. Maachianus 

 Ar. Benn. (P. serrulatus Beg. et Maack., non Opiz, nee Schrader), 

 but specimens in fruit are so rare that it is not perhaps safe to 

 assume they do not occur. 



Though so common in at least fifteen of the United States, 

 especially in Massachusetts, its life-history has yet to be written, 

 and would afford an excellent study. But this must be done in 

 the field or by cultivation; dried specimens only afford a few 

 phases of plant-life, and that mostly in the condition in which 

 they can best be specifically determined ; the spring and winter 

 states are rarely represented. Mr. Hill (/. c) considers this species 

 one of the best defined and least variable of North American 

 Potamogetons. An additional station to those on record where it 

 has been found in fruit is " Duck Lake, Whitehall, Mich./' Hill sp. 

 Before 1880 only one fruit was known, but in that year it was 

 found by Mr. Faxon in Massachusetts, and in 1889 by Prof. 

 Macoun in the Somas Biver at Alberni, Vancouver Island. 



P. SPATHULiEFORMis Morong in Mem. Torr. Bot. Club, iii. pt. 2 



