2/2 



NATURE 



[April 28, 192 1 



bushes of boulder-strewn stream-beds and river- 

 banks, and the willow thickets of the Jaman-tal. 



In his careful ecological study of the results of 

 the Danish expedition, Paulsen, with arguments 

 that compel conviction, suggests that these 

 "stony wastes " scarcely fall within the "desert " 

 category. Fedtschenko's " Eurotia desert," in par- 

 ticular, Paulsen prefers to regard as "fell," using 

 this term with a connotation corresponding with 

 that of the word "forest," to signify that the 

 plants involved show adaptation to cold and snow- 

 rather than accommodation to drought and heat. 

 High Pamir plants display few expressions of 

 adaptation to drought ; their habit and their his- 

 tology alike suggest that they are more influ- 

 enced by strong light than by dry air. Further, 

 they agree more closely, on the whole, with alpine 

 than with arctic plants, and their structure sug- 

 gests that they are affected more markedly by 

 the altitude at which they grow than by the 

 climate they have to endure. 



The formations recognised by Paulsen for the 

 dry High Pamir are four in number, and are 

 named, from characteristic species in each, the 

 Trigonella-, the Eurotia-, the Arenaria-, and the 

 Voa affenwafa-formations. Of these the Trigon- 

 ella-formation is defined as the vegetation, largely 

 xerophytic, of the valley-floors of the High Pamir, 

 and the Eurotia-formation as the xerophytic 

 vegetation on mountain-slopes with a southern or 

 a western exposure ; the Arenaria-formation is 

 a special association, only seen well-developed 

 near Lake Jashil-kul, which is a transition between 

 the Trigonella-formation and the mesophytic vege- 

 tation on mountain-slopes exposed to the north ; 

 and the Poa affenua/a-formation includes all the 

 mesophytic associations of mountain-slopes with a 

 northern aspect. In his comparison of the two 

 systems, Paulsen regards Fedtschenko's alpine 

 meadows as identical with his own Poor attenuata- 

 formation ; unites Fedtschenko's damp-meadows 

 and salt-marshes in what he himself terms 

 ''swamp-meadow"; and recognises Fedtschenko's 

 "woody formation." As regards Fedtschenko's 

 " Eurotia desert " and " Bluff " associations, Paul- 

 sen's concordance is of a tentative nature; he sug- 

 gests that the former may be his own Trigonella- 

 formation, the latter his own Eurotia-formation. 

 Clearly, however, the Eurotia desert of Fedt- 

 schenko includes the Trigonella-, the Arenaria-, 

 and the Eurotia-formations of Paulsen, who ap- 

 parently does not regard Fedtschenko's "Bluff" 

 association as a definite entity. There is nothing 

 save Fedtschenko's expression "and so forth" 

 to support the suggestion that this author's 

 "Abhange u.s.w." may include mountain-slopes 

 with a southern exposure ; the " Bluff " association 

 plants mentioned by Fedtschenko are not met with 

 on the slopes to the north or east of a flat valley- 

 floor. Interesting though this particular plant- 

 association may be, a student of the High Pamir 

 vegetation may be excused if he regards it as 

 being, like the "woody formation " in the boulder- 

 strewn river-beds, an intruding element that, 

 favoured by special conditions, has extended up- 

 NO. 2687, VOL. 107] 



wards from the narrow valleys of the Low Pamir. 

 For the sake of convenience we may also exclude 

 the floating and submerged plant-associations of 

 the marshes and lakes, not as being devoid of 

 interest, but as not being distinctive of the High 

 Pamir, 



When the vegetation characteristic of these 

 Pamirs is regarded from the English traveller's 

 point of view, account must be taken both of the 

 open surface of the valley-floor and of the slopes 

 that rise from it on either hand. In dealing with 

 the open surface we may begin with the green 

 ribbon of vegetation that skirts the streams and 

 fringes the lakes. This green belt includes two 

 marked plant-associations : water-meadows or 

 marshes, characterised by the presence of tufted 

 sedges ; and haughs of mountain meadow grasses 

 mixed w^ith which are many gay alpine plants. 

 These High Pamir marshes may furnish, all told, 

 some forty species, whereof a score are to be ex- 

 pected in any single Pamir. The haughs may 

 supply about fifty species, of which one-half to 

 two-thirds may be present in any one valley. These 

 two plant-associations constitute one plant-forma- 

 tion, composed exclusively of mesophytic plants. 

 In this respect it does not differ from the Poa 

 attenuata-iormsition of the slopes with a northern 

 exposure that bound the valley to the south or 

 the west. Though as rich in species as the rest 

 of the valley-floor, this green belt is less interest- 

 ing ecologically than the open surface above the 

 Bluff. 



That open surface, notwithstanding its bare ap- 

 pearance as seen from above, is far from being 

 devoid of vegetation. If the flora be of a poor 

 type, that type is highly developed, and is made 

 up of scattered tufted xerophytes with an admix- 

 ture of cushion-plants. The individual plant- 

 clumps are often a yard or more through, and 

 usually a pace or two apart, so that, where 

 vegetation occurs at all, it clothes approximately 

 half the ground, though scattered irregularly over 

 the valley-floor are many bare stretches of hard 

 sand and shingle, variable in extent, and often 

 coated with a saline efflorescence. Sometimes 

 such saline spots sustain a few halophilous species, 

 which thus constitute a distinct plant-association, 

 while in the vicinity of the hot springs that occur 

 in some of these high valleys a few peculiar 

 species constitute yet another association. Ex- 

 cluding these two relatively unimportant elements, 

 the vegetation of the High Pamir valley-floors, 

 taken as a whole, is remarkably uniform through- 

 out the region, and may be regarded as a distinct 

 plant-formation. The number of species involved 

 varies somewhat in different valleys ; thirty may 

 perhaps be a fair expectation for a particular 

 Pamir ; fifty is about the number for the High 

 Pamir as a whole. The formation is, then, about 

 as rich in species as the riverside mesophytic one, 

 but in this case the species most plentiful in any 

 single Pamir are, with few exceptions, those most 

 plentiful in all the valleys. 



Along the route followed by the Danish expedi- 

 ' tion and the Russian travellers the slopes that 



