160 VIGNETTES FROM NATURE. 



droughts by virtue of their superior fleshiness 

 would occasionally cross with one another, 

 either by wind-fertilisation or by stray visits 

 of pollen-hunting midges, it is clear that in 

 the course of time a new succulent species 

 would be slowly evolved. As a matter of 

 fact, the goosefoots have really given origin 

 to several such sand-loving weeds, each of the 

 principal groups having probably a separate 

 origin from some particular kind of strictly 

 terrestrial goosefoot. 



After the saltwort had grown succulent it 

 began also to grow prickly. For sand-loving 

 plants are naturally exposed to very great 

 danger from herbivorous animals, against 

 which they are accordingly compelled to pro- 

 tect themselves by some hostile device. In 

 the first place, there is comparatively little 

 vegetation on sandy spots, so that each plant 

 runs an exceptional chance of being eaten. 

 Then, again, the succulence and juiciness of 

 sand-haunting weeds make them particularly 

 tempting to thirsty animals, which are sure to 



