December 1, 1896.] 



KNOWLEDGE 



271 



entirely on vegetable food, such as the lemming, hare, 

 goose, musk ox, and reindeer. 



Although no seed is produced in the higher latitudes, 

 seed taken there germinated and grew during the summer 

 in a temperature almost constantly as low as thirty-three 

 degrees Fahrenheit. As no seed is produced, it follows 

 that the present Arctic vegetation must be the remnant of 

 a former more extensive flora ; but, apart from this fact, 

 there is abundant fossil evidence, both animal and vegetable, 

 of very dil&rent conditions from the present. 



Another curious point in connection with Arctic vegetation 

 is the fact that only the surface of the soil thaws during 

 the short summer, so that the roots of plants are in a 

 medium bordering on the freezing point. This phenomenon 

 may occasionally be seen exemplitied in this country, where 

 one portion of a grape vine, for example, is under glass 

 and the other out of doors. The sheltered part, in spite 

 of external cold, will grow and produce fruit, whilst the 

 exposed part will remain dormant until spring. 



I have not much space left for the discussion of the 

 altitudinal limits of flowering plants, but a few of the 

 leading facts will suffice. Contrary to what might have 

 been expected, considering the latitude, it is in the 

 region of the greatest elevation — in North India and 

 Central Asia — where flowering plants reach the highest 

 levels of any part of the world. The comparatively 

 recent explorations of Conway, Rockhill, Thorold, and 

 others, have yielded some highly interesting results. 

 The collection made by Dr. Thorold may be taken as an 

 illustration of this high-level vegetation. Dr. Thorold 

 accompanied Captain Bower across Tibet from west to 

 east, from Ladak to China. The route lay between 80^ 

 and 84° north latitude, at an average altitude of fifteen 

 thousand feet, or about the same as the summit of Mont 

 Blanc. As may be imagined, the climate is very severe 

 and the vegetation exceedingly scanty ; yet upwards of a 

 hundred species of flowering plants were collected, with 

 few exceptions belonging to genera represented in the 

 British flora. Considering the altitude, this number is 

 large as compared with what is found in other parts of the 

 world ; but when we reflect that as many species may be 

 found on an acre of ground in this country, and that those 

 hundred or so species were the fruits of five months' march 

 through twenty degrees of longitude, we begin to realize 

 the extreme poverty of the flora. Throughout this long 

 journey, not a tree, not even a bush, was seen ; none of the 

 plants were more than a foot high, and most of them 

 not more than two or three inches. They nowhere formed 

 a carpet, but occun-ed singly or few together, and at long 

 intervals. Plants having large descending roots, a rosette 

 of leaves flat on the ground, with flowers nestling close in 

 the centre, are characteristic of this region. Many of 

 these belong to the thistle family. There are also butter- 

 cups, larkspurs, poppies, scurvy grass, saxifrages, asters, 

 dandelions, wormwoods, primroses, gentians, and grasses. 

 Contrary to what is the case in the Arctic regions, about 

 half of the species are peculiar to this great upland country. 

 About sixty of them were collected at altitudes between 

 seventeen thousand and nineteen thousand feet, and of 

 these half a dozen were found above eighteen thousand 

 feet. One only was met with at nineteen thousand feet. 

 This is SdKssitrca tiiiliirti/hi, a plant densely clothed with 

 woolly hairs. A species of the same genus inhabits the 

 mountains of the North of England and Wales. 



[In the series of articles of which this is the last, I have 

 almost confined myself to a statement of facts of the 

 present distribution of plants over the surface of the earth. 

 I have pointed out that the domestic weeds and cornfield 

 weeds of Europe have spread in temperate and sub-tropical 



countries almost as widely and rapidly as man, for the 

 greater part unintentionally introduced by him with the 

 seeds of his cultivated plants ; and I may add that there 

 has been no counter current to speak of. This is to be 

 accounted for by the fact that in the uncivilized countries 

 now colonized by European races, there was little or no 

 cultivation and there were no roads ; consequently there 

 were no plants that had adapted themselves to the 

 conditions of life connected with civilization. It is true 

 that a few exceptions might be named, but they prove the 

 general statement. Many readers, doubtless, wiU remem- 

 ber the American water- weed (Anncliaris canadensis), which 

 invaded this country about fifty years ago, and spread at such 

 a surprisingly rapid rate that it soon choked ponds, ditches, 

 and brooks from one end of the country to the other. 

 This has since lost much of its former vigour, and is now 

 more easily combatted. 



I also alluded to the planting of remote islands bv 

 means of oceanic currents, tidal waves, and birds con- 

 veying seeds which retain their vitality after long immer- 

 sion in sea water, or after passing through the intestinal 

 canal of a bird. But these agencies, much as they may 

 have eflfected, count for little as against the great physical 

 changes which our earth has undergone during the count- 

 less years which must have elapsed since the first fossil 

 remains were deposited and petrified, which now serve as 

 history — undated, it is true — of a past that is unfathom- 

 able.! 



OUR FUR PRODUCERS.-VI. 



EODENTS, UNGULATES, AND MARSUPIALS. 



By E. Lydekker, B.A.Cantab., F.R.S. 



NUMERICALLY a high position in the fur trade 

 is occupied by the skins of certain species of 

 the order of rodents, or gnawing mammals, 

 although several of these are of little value 

 individually, and their importance in the market 

 is solely due to the numbers in which they are collected. 

 Among such rodents we may first notice the common 

 squirrel, which has an extremely wide geographical range, 

 extending from England in the West to .lapau in the East, 

 and reaching northwards to Siberia. In the first half of 

 the century the trade in squirrel skins was enormous, over 

 two and three-quarter millions havmg been imported into 

 this country in the year isBO. Since that date the numbers 

 have declined, although it is at present impossible to obtain 

 exact data ; but that the trade is even now very consider- 

 able may be gathered from the fact that the annual import 

 from Ockotsk alone to London varies from fifty to a hundred 

 thousand. Squirrel skins are subject to considerable 

 variation in colour according to locality, those from the 

 Russian province of Kazan having the red tinge very 

 strongly pronounced, while to the east of the Urals greyer 

 species are met with ; and in parts of Siberia and Japan 

 the general colour is slaty blue or blackish, the ears and 

 tails being almost entirely black. The darker the fur the 

 greater the value of the skin. The great squirrel-dressing 

 centre is Weissenfels, in Germany, where some establish- 

 ments prepare half a million skins annually. The skins 

 are cut up into backs, bellies, and tails ; and while the 

 first of these are used for capes, trimmings, and the linings 

 of gloves, the second form the bluish while linings of 

 opera and other cloaks. Tails, on the other hand, are 

 made up into fringes for mantles, or into boas : while the 

 hair, when removed, is used for the manufacture of the 

 so-called camcl's-hair paint brushes. Although a few of 

 the larger skins are dyed in imitation of marten, squirrel 



