250 MB. G. BENTHAM ON E17PHORBIACE J2. 



dages, but becomes more and more oblique, with unequal glands, 

 those on one side often much reduced or even deficient. The 

 extreme forms of this section almost pass into the peculiarly 

 American genus Pedilanthis, consisting of about fifteen species, 

 the most divergent of which may be taken as the last stage of 

 evolution in this direction. These species do not appear to be 

 very abundant in varieties or in individuals ; but they are not marked 

 by any very prominent distinctive characters, they leave no great 

 gaps between them, and show no approach to any other old group 

 or genus, thus giving no evidences of a comparatively remote 

 antiquity. 



There remains the very natural and well-characterized section 

 Anisopliyllum , of which Boissier enumerates 176 species, a number 

 which might without violence be extended to above 200 or reduced 

 to little more than 100, so great is the variability of many of them. 

 Collectively they are cosmopolitan ; and individually many are 

 very widely spread ; at least three (E. pilulifera, E. serpens, and 

 E. thy mif olid) are nearly equally spread over the ~N"ew and the Old 

 World ; and they afford very few data on which to found conjec- 

 tures as to the origin and chief centres of the tribe. The species 

 belong almost exclusively to that category of annuals or plants of 

 short duration which ripen their seeds in great profusion in the 

 season which gave them birth, or at the worst have but one dead 

 season to pass through before maturity. Their chances of acclima- 

 tization (i. e. of producing races better suited to the soil, climate, or 

 social conditions of the territory they have invaded) are thus infi- 

 nitely greater than in the case of trees, shrubs, or long-lived peren- 

 nials/which have in their primitive state to bear through a number 

 of varied seasons before they are ready for reproduction and the 

 chances of variation. On the other hand, these annuals are ex- 

 posed to chances of destruction in the successive stages of seed, 

 seedling, and plant they have to go through every year, very 

 numerous in comparison with those which affect the arborescent, 

 frutescent, or perennial plant, which, having once established its 

 root or stock firmly in the ground is not to be annihilated by in- 

 juries to its aerial stem or foliage. Such annuals have, in fact, 

 often been known to have extended, contracted, or changed their 

 areas with great rapidity ; and in their case, therefore, present 

 distribution gives but very little clue to their ancient history. 

 In the case of Anisophyllum, moreover, many of them are mari- 

 time plants or weeds of cultivation, both of these classes enjoying 



