1752 A TEXTBOOK OF THEORETICAL BOTANY 



cultivated in temperate regions on account of its use in textiles and for the 

 long, strong bast fibres. In some countries it is grown for the narcotic 

 resin obtained from the leaves, which acts like opium as a drug and a stimu- 

 lant. From it is made an intoxicating drink, haschisch. It is also smoked, 

 with or without tobacco, under the name of marihuana. In small quantities 

 it produces excitement but increasing doses cause delirium and finally 

 catalepsy. Stringent laws keep a check on its use and recently the sale of 

 seed in Great Britain has been stopped. 



The family Eucommiaceae is monotypic and contains the single 

 genus Eiicommia which is of some economic interest. E. idmoides is a tree 

 with alternate leaves and naked, unisexual flowers. It yields latex contain- 

 ing caoutchouc, while the bark produces a medicine valued by the Chinese. 

 It has the distinction of being the only rubber-producing tree which is 

 hardv, but its latex is, unfortunately, of no commercial value. 



SALICALES 



Salicaceae 



The family includes two types of shrubs or trees common in Britain 

 which are collectively spoken of as the Willows and Poplars. Among the 

 Willows we may mention Salix caprea (Common Sallow or Goat Willow) 

 (Fig. 163 1), S. fragilis (Crack Willow), S. babylonica (Weeping Willow), 

 which is not a native, and S. viminalis (Osier). Several dwarf species such as 

 S. reticulata and S. herbacea are common as alpine plants and are also found 

 in the Arctic. Among the Poplars found in this country are Populiis nigra 

 (Black Poplar), P. alba (White Poplar), P. tremida (Aspen) and P. nigra var. 

 italica (Lombardy Poplar) which is a fastigiate variety of the Black Poplar. 



The plants are either large trees or shrubs, with alternate leaves which 



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The Salicales are Archichlamydeae in which the flowers are unisexual 

 and are produced in catkins. Each flower is subtended by a bract. The 

 male flower is very reduced and consists of two or more stamens: the female 

 flower of two carpels which are united to form a one-celled ovary with 

 parietal placentation. The ovules are numerous and the seeds are covered 

 with fine hairs. There is no endosperm and the embryo lies straight. f 



The order includes the single family Salicaceae, a point on which all 

 authorities agree. They do not agree however on the systematic position 

 of the order. The older view, which was supported both by Bentham and 

 Hooker and also by Engler, was to relegate them to a separate group, the 

 Apetalae, which were considered more primitive than the Archichlamydeae 

 and closely related to the Gymnospermae. This view was based upon the 

 very simple, incomplete flowers which they possessed, which were con- 

 sidered to be primitive. The more modern view as expressed by Hutchinson 

 is to consider the flowers specialized but reduced and to relate them more 

 closely with the Rosales, through the Hamamelidaceae. There is certainly 

 much in favour of this view, which we shall follow. 



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