loS ANNALS OF SCOTTISH NATURAL HISTORY 



involves. No herbarium specimens can answer the queries 

 (unless specially collected) like the growing plants. Fortun- 

 ately Mr. Macvicar's specimens of this plant show well the 

 varying stages of growth, and it is these young growths that 

 at once show the specimens cannot be prcelongus " pure and 

 simple." 



It may be urged (and rightly) " but how do you know 

 how these species differ among themselves ; may not these 

 specimens be only an extreme form of the species?" In 

 answer to this I may say I had prcelongns growing for eight 

 years in my garden ; it was watched week by week (along 

 with alpinus and Griffithii}, and I never saw anything 

 approaching to these specimens. 



P. prcelongus in its usual form occurs in many lochs 

 in Moidart, " Lochs Bealachna, Garisha," etc. ; and the 

 specimens are in no way different to others from its area of 

 distribution. 



fjab. Loch-na-Craig-dhui, Ardnamurchan, and Loch 

 Dow, Moidart, Argyllshire. This first loch has a stream 

 running through it from Loch Sligneach, and discharges its 

 waters by the Allt Eas-an-Taileia into Kentra Bay. 



Differs from prcelongns (to which it is most nearly 

 related) by the leaves being distinctly tapered into the 

 footstalk, and in the young growths with a distinct petiole, 

 the stipules much less persistent (even in the young growths), 

 in the young leaves never hooded at the apex (and not 

 always so in the mature growth), or even if slightly so, not 

 splitting as they so often do in prcelongns, and in the structure 

 of the venation of the leaves, which is between prcelongus and 

 polygonifolins. In the young state the aspect of the leaves 

 is very like the submerged elongated leaves of polygonifolins, 

 except that the apex is rounded, instead of pointed (or 

 subacute). 



None of the specimens have flowers or fruits. 



Taking a series of leaves and comparing them with 

 those of prcelongns, they show as under : 



X P. Macvicarii. P. prcelongus. 



3 principal nerves. 3 principal nerves. 



8 lesser do. I I lesser do. 



