480 



CV. NAIABACE^. 



\_Potamogeton. 



Lakes and ponds. Forfarshire and BGrwiekshire. I/.. 6,7. 

 So similar to our var, a. of the last that we know no distmguishincr 

 character except the smaller flowers and fruit, and the achenes beino- 

 quite rounded on the back after the cuticle has been removed: when 

 this is not removed, they sometimes appear 3-ribbed externally. 

 Kunth (En. iii. p. 136) iinites them. 



■/• 



*** Lmves alternate^ all linear^ submerged ; stipules free. 



4. P. trichoides Cham, (hair-like P.) ; leaves sub-setaceous, 

 1-nerved finely pointed, peduncles elongated, spike at length 

 somewhat lax, stem capillary nearly terete. Ch. and SchlecliL 

 1. c. p. 175, 



Ponds and ditches, Bixley near Norwich, %. 7, 8, — We have 

 seen no British specimens^ nor are we at all satisfied that the foreign 

 ones are specifically distinct from the next species, with which 

 Kunth also is inclined to unite them. The fruit has an obscure tooth 

 on the ventral suture near the base, which has not been observed in 



P. pusillits, 



5. P. pnsillas L, (small P.) ; leaves narrow-linear 3-5- 

 nerved with obscure connecting veins, peduncles 2—3 times 

 longer than the somewhat lax spike, stem slightly compressed. 

 — a, leaves 3-nerved, nerves in the middle between the midrib 

 andthe margin. E. B. t. 215, — ^. leaves broader with an 

 accessory nerve on each side between the margin and the 

 primary lateral ones. P. compi^essus i,: -E. B. t. 418, 



Ditches and still waters. If.. 7.— The leaves are more or less 

 acute ; the spikes oblong, compactor a little interrupted. We quite 

 ao-ree with Chamisso and Schlechtendal, who unite the P. compressus 



with P. pusillus, 



6. P. gramiiiens L. 

 obtuse 3-nerved with 



(grassy P.) ; leaves broadly linear 

 few and obscure connecting veins, 



peduncle scarcely Ioniser than the oblong oval dense spike, 

 stem slightly compres'sed. E. B. U 2253. P. obtusifolius 

 Mert and Koch. 



Ponds and ditches. Amberley, Sussex ; Orford, near Warrington, 

 Lancashire; Arbury Hall, Warwickshire:; Deptford, Norwich, York- 

 shire. Possil marsh, near Glasgow ; Kincardineshire. 7f. 7. — 

 Nearly allied to the last, but stouter, darker-coloured, and with short 

 peduncles, scarcely longer than the stipule of the leaf from the axil of 

 which thev spring. The middle nerve or rib is accompanied by many 

 parallel oblong reticulations both in this and the last species ; but 

 there are none of the numerous longitudinal parallel intermediate 

 nerves seen in the two following. Occasionally the peduncles are 

 nearly twice the length of the spike, when it becomes very difficult to 

 distinguish this from var. jS. of the last species, with which it agrees 

 in general appearance ; but we believe that the latter has always the 

 two supplementary nerves, wliereas P, gramineus has the leaves only 



«** Urn 



i P. c; 



lite wavei 

 1,1012. 



Ditches 

 llidened i 



10. R 



\ 



aiK 



nerres. 



J 



Ditches 



s not s 



1 



\^ 



