30 Morten P. Porsild. 



to tlu' hottom diiriiii,' tin' wintfi-. Tlic IimiltIIi dl' llicir vci^fclatix r |)i'ii(i(l 

 espociiillv (It'ptMids upon tlic condilinii ol' Ihc spring ainl thc ;iiit iiniii. 

 In oaso ol' ;• told spriiiu llic ieo aloiii!: tlio pondsiiores is rat her loncj 

 iti iMt'Jtiui;. ;md il" tlir aiiturnii sots iii i-arly, thc ponds are (|iii( kly l'rcezing 

 iipai;ain. hiirint; siicli iiiifoi-tunate summers Ihc Potamogetonaceae (and 

 otlnT watt'rplants) liardly attain to floworiiig and not al all hi fnicli- 

 ficalion. tlioy reprodiice by continuous t'orminj? of Avinterbuds. In more 

 fortimate seasons flic poriod ol" vegetation in tlic same wator will last 

 long enougli Tor tin' l'orming of llowers and Iriiits. Bul I his is, in our 

 area, an cxccption, all the t'ollowing species being decided so ut horn 

 types willi their nortli limit hero. 



As the climatie conditions in the ar^tic Jaiuls xai-y Ironi yrar lo 

 year. and as the amount of warmth necessary to the vital iLuiLlions 

 of the piants is not oniy relatively, but also absolutely inconsiderable, 

 it is no wondei- Ihat the same species on the same latitude is sometimes 

 found flowering, sometimes quite sterile. 



± 21 Potamogeton alpinus Balb. 



Itivneq at Holsteinborg (3ti^58' (\V. c^' IL), only once collected 

 ht'ri': thc north limit of the species. 



Ktiown Ironi Godthaabfjord and somo plares in the extreme 

 South <"in'i'idnnd. 



± 22. Potamogeton graniineus L. 



In a small lakc ncar tho river lo tho head of S. Slidiiirjur.I ca. 67° (Jens.) 

 only once found liere. The north limit of the species. 



Elsewhere only known from the southmost part of Greenhind 60° — 61°. 



Note: The species is also recorded from Rode Elv at Godhavn 6i»°15' by Rev. 

 .Sitrensfii. Tlie s|)ecimens were determined, and of course correclly, \<y Prof. L. Iv. 

 RosF,\vi\<iF., hiit from where it ori>finates. wc (aniiot say. It can not he from 

 Rode Elv. tilis heiiiK a «uld clacier-torrent in wliicii no plianerogamous water- 

 filiuit is ahle lo thrivc;, least of all a Potamogeton with a soulherly dislrihulion 

 as P. grainirn'us. 



1 2;]. Potamogeton mucronatus S(uii\h. (/'. /-'rirsti Hieu.). 



Diskofjord in small jiuii<ls al Ei|aliin},'Mil llivncrc (W32' (P.) del. Prof. C. 

 Rai NKi.tR. Aflerwards not seen in Greenland. 



The specimen was sterile. 



1 24. Potamogeton obtusifolius .\I. ^ K. 



Thc <lislricl of Egedesminde: Ikainiut iiil.j in Niva(| Bugt 68°40' (Kr.). 

 The specimens were sterilo. 



