160 NATURAL HISTORY OF PLANTS. 



to the fundamental parenchyma of the plant, lengthening immode- 

 rately, vertically, and also laterally, in such a manner as to insinuate 

 themselves into the intervals of the other anatomical elements ; their 

 contents must penetrate into the latter according to circumstances 

 which are still imperfectly known. But what seems certain is that 

 the quantity is not always ihe same in the lactiferous reservoirs. The 

 latex is sometimes opaline or almost completely uncoloured, and 

 sometimes opaque and milky. It is often rich in caoutchouc, and 

 is usually distinguished by another peculiarity, the presence of 

 small retilinear, bacteriform, linear bodies, whose reaction is the 

 same as starch.^ There are in certain Euphorbiacece saps of quite 

 another nature ; they are coloured liquids, usually rose purple. 

 They are met with in many flowers, notably m. Tournesolia^ Mercurialis, 

 Lasiocroton, Plunkenetia, or in the seeds, pretty often also in the 

 organs of vegetation. 



The Euphorbiacece^ actually known to the number of nearly three 

 thousand two hundred and sixty-two species, are very unequally 

 dispersed over the entire surface of the globe. The genus which 

 extends over the largest area is the genus Euphorbia, which exists 

 everywhere, as well in warm regions as in cold and temperate 

 countries, to the north of Europe and Asia on one side, and, on the 

 other, to the extreme south of Africa, Patagonia, and New Zealand. 

 The number of genera well known to be allied to the family 

 and which belong properly to the old world, are seventy-four, 

 and America has only forty. The genera common to both are 

 therefore twenty-three, but these are in general the largest and most 

 numerous in species, for they comprise nearly two thousand four hun- 

 dred and thirty, while the forty purely American genera, nearly all 

 less important in number of species, include only seventy -two. In the 

 genera peculiar to the old world, we count five hundred and eighty 

 species. 



1 Hofineister admits that the grains of starch protoplasmic suhstances ; but there are some of 



of the latex of certain Euphorliacets constitute these substances in the latex (Sachs) : so that 



an exception, as they do not cease to grow the exception is only apparent, 

 when they are no longer in contact with the 



