CHINESE TREES AND SHRUBS. 



219 



In their vivid whiteness and grace, the leafless stems make one of the 

 most striking of winter pictures (Fig. 48). Another very handsome 

 Rubus is called thihetanus or Veifchii. Its stems are of a bluer, less 

 vivid white than those of Giraldianus, but the foliage, in its fern-like 

 cutting, is perhaps the handsomest among these new species. 



Among Viburnums there are several of very distinct appearance. 

 Viburnum rhytidophy Hum, with its curiously wrinkled leaves, is by now 

 known to most cultivators. Its garden value is in its fruits, which turn 

 first brilliant red, then black. As an ordinary evergreen for shrubberies 

 or for grouping it has a defect in winter. If planted in a position at 

 all exposed it looks during cold spells shrivelled and extremely sorry 

 for itself. With the return of spring, however, it loses its dejected 

 appearance and the leaves regain their fulness. It sets its blossoms 

 in autumn, and they remain in the bud state uninjured all the winter, 

 opening normally in May. 



V. Henryi is another evergreen species, rather thinly branched 

 and sparse of leaf, but very handsome when laden with red fruits. 

 V. utile is more attractive for its blossom. V. Davidii represents 

 a very distinct group of Viburnums with strongly 3-veined leaves 

 and blue fruits. V. coriaceum, too, with pink cylindrical flowers, 

 differs from every other species in cultivation by the thin waxy layer 

 on the leaves, which turns white when rubbed, or when the leaf is 

 bent. 



One of the most interesting facts in connexion with the distribution 

 of plants on the face of the globe is the close affinity of the flora of 

 China and other parts of North-eastern Asia with that of eastern 

 North America. At an earlier stage of the world's history the land 

 connexion between North America and Asia in the neighbourhood of 

 the Behring Sea and Behring Strait appears to have been extensive, 

 and the temperate flora reached much nearer the North Pole than 

 it does to-day. That part of the globe where these two continents 

 nearly meet, now too cold to support much vegetation, was covered 

 with a fine sylva. As the polar ice-cap descended, the warmth-loving 

 vegetation was squeezed gradually southwards, one part passing 

 eastward into North America, the other westward into Asia. The 

 Rocky Mountains appear to have acted hke the points on a railway 

 and diverted the receding flora to the eastern side of America. At 

 any rate, the flora of western North America, although geographicaUy 

 much nearer that of China than the eastern one, is far less closely 

 related to it. Such well-known genera as Magnolia, Hamamelis, 

 Catalpa, Stewartia, and Wistaria are but a few that illustrate this 

 interesting phenomenon of the same genus being represented on 

 the Atlantic side of North America and in North-eastern Asia, 

 but neither on the Pacific side of North America nor anywhere 

 else. 



One of the most interesting things in connexion with Wilson's 

 discoveries and introductions from China has been the production 

 of further evidence in support of the theory thus crudely defined. 



