34 NOTES ON PONDWEEDS. 



When growing in shallow water, barren states of the plant look 

 like a miniature form of P. coriacens, but the resemblance is merely 

 suj^erficial ; for shallow-water states of the latter plant do not at all 

 resemble P. varians, but, on the other hand, approach P. Zizii. 

 The early spring growth of P. varians is like that of P. heterophyllus, 

 to which plant it is most nearly alhed, but differs in its more diffuse, 

 less submerged growth, and in the compressed circular- outlined 

 fi-uit. From F. Zizii it is clearly separated by the small compressed 

 fruit, and usually by its much smaller size ; but in luxuriant states 

 of the plant, and especially late in the season, barren shoots are 

 produced which closely approach autumn states of P. Zizii. 



P. varians has been observed in America for some years, but I 

 am unable to give the history of its discovery in that country. The 

 earliest-gathered specimen I possess, through the kindness of the 

 Eev. T. Morong, is labelled by him : — 



" Potamogeton gramineus L. 

 Yar. ? spathidcpformis Bobbins. 

 P. spathaformis Tuck. 

 P. varians Morong. 



Coll. T. M. in Mystic Pond, Medford, Mass., 

 July 10, 1879." 



I here copy from the 5th ed. of Asa Gray's ' Manual of the 

 Botany of the Northern United States,' 1879, Dr. Eobbins' descrip- 

 tion of var. ? spatJnilo'formis: — '' P. gramineus L., var. ? spathidcpformis 

 (P. spathafornds Tuckerman in herb.). Branches scattered; floating 

 leaves obovate or oblong, with a larger point ; submersed ones 

 spathulate-oblong, obtuse, mucrouate, sometimes recurved; spikes 

 large and densely flowered. — Mystic Pond near Boston, Tuckerman. 

 The fruit is lacking to prove its rank." 



This description well agrees with the fenland plant, except as re- 

 gards the flower-spikes, but those in Cambridgeshire specimens from 

 Blockslock Moor, near Mepal, are certainly both large and densely 

 flowered. This Mepal plant is the form or state mentioned above 

 as producing autumnal shoots so like those of P. Zizii. It is also 

 remarkable for having a tendency to produce peduncles which are 

 forked from the middle, each limb of the fork subtended by a slender 

 bract, and bearing a flower- spike. 



Of the American P. varians, Mr. Morong whites: — "It never 

 did form fruit, so far as known, and so has sometimes been con- 

 sidered a hybrid. I am not satisfied whether it should rank as P. 

 gramineus or P. Zizii. Dr. Eobbins rather inchned to the former 

 . . . but I am more inclined to place it with Zizii, I must confess." 

 This opinion of the learned American botanist is in accordance 

 ■with that of Dr. Trimen, who quotes in the ' Journal of Botany' for 

 October, 1879, ''spatJurfvrmis" as a probable synonym of P. Zizii, 

 and says: — "To judge from specimens in the British Museum, 

 labelled 'P. spatha/ormis Tuckerm. herb.,' the P. gramineus var. 

 spathaj'ormis is also referable to P. Zizii.'' Now these opinions 

 carry great weight, but I think the small drupelets, which approach 

 those of P. heterophijilus, must place the American and British 



