54 
furnished by Mr. Fryer and collected by him in Cambridgeshire, 
England, where the plant is common. Fruit broadly obliquely 
obovate, obtuse at base, the largest 2 lines long by 1 34 lines wide, 
prominently keeled and with rounded lateral ridges on the back; 
face nearly or quite straight, sometimes gibbous at the top; style 
facial, erect; embryo outline obovate, the apex pointing slightly 
inside of the basal end. The shell of the drupe is exceedingly 
thick and quite hard. 
First found by Mr. E. J. Hill in ponds at Manistee, Mich., and 
subsequently collected by myself in the same locality. Also col- 
lected by Mr. Hill in the Channel Islands, St. Mary’s River, Mich. 
Mr. Hill takes especial notice of the tubers by which this species 
is frequently propagated. This method of propagation it has in 
common with P. pectinatus, to which it is closely allied. (Plate 
=.) 
37. POTAMOGETON Коввіхѕи, Oakes, Hovey's Mag. May, 1841, 
px 
Stems stout, widely branching, 2-4 feet high, from running 
rootstocks sometimes 10 or I2 inches long. Leaves 3-5 inches 
long, 2-3 lines wide, acute, finely many-nerved, crowded in 2 
ranks, minutely serrulate under the lens, auriculate at the point of 
attachment with the stipule. Stipules with the adnate portion and 
sheathing base of the leaf about 77 an inch long, the free part from 
1% to 1 inch, acute, persistent, white, membranous, mostly lacerate. 
Peduncles 1-3 inches long, the infloresence frequently much 
branched and bearing from 5 to 20 peduncles. Spikes interrupted, 
15—34 inch long, flowering under water, but the rarest of all our 
North American species to form fruit. Itis propagated very ex- 
tensively by fragments of the stems, which throw out many root- 
lets from every joint. I have seen such rootlets from 6 to 10 
inches long on floating specimens, and even a stem standing up- 
side down in the mud and growing apparently as well as in the 
normal position. "Very rarely in years when the waters are low, 
the flowering spikes rise above the surface and perfect a few fruit. 
Dr. Robbins never saw but one.fruit, which was collected many 
years ago in Oregon by Hall, and this was split in two, Prof. D. C. 
Eaton taking one-half and Dr. Robbins the other. In the year 
