HORN EXPEDITION — NARRATIVE. 15 



wliich we travelled are species of Portnlaca, popularly known as munyeru, and 

 various species of Claytonia. Tiiese <^row in little clumps, lying low down upon 

 the ground, and remain soft and juicy when everything else is dry and withered. 



There can, I think, Ije littlt^ douht but that this switch-like structure of 

 leaves and leaf-stalks, together with, in the case of the desert oak {Casi/arina 

 Descaiiica/in), the loss of leaves, and the substitution for them of little still' green 

 twigs, and also, in other plants, the development of hard, (hoi-ny processes around 

 the seed-cases, is simply due to an adaptation to climatic influenc(\s, and has, in 

 the case of the Central Australian plants, very little, if indeed anything whatever, 

 to do with protection against animals. 



In the first place, there are comparatively few animals to feed upon them ; 

 kangaroos and wallabies and other plant-eating marsupials do not exist in 

 anything like sufficient numbers to keep the plants down ; and then those which 

 are succulent and edible, such as the munyeru and Claytonias, and in no way 

 protected against animals, .so far as can be seen and judging from the way in 

 which they eat them, thrive just as well as the spiked and thorny plants. 



What appears to be most probably the case is, not that the prickly growth is 

 brought about in any way as a protection against predatory animals, but that it 

 and the succulent development as well, are adaptations to suit climatic environ- 

 ment. If animals, so to speak, want to feed upon these climate-proof plants, then 

 they must become fitted to do so. None of these Central Australian plants, 

 which are as spiny as they can well be, are in the least thereby protected against 

 such an animal as the camel, which will, with relish, munch away at the mo.st 

 thorny Acacia {^Aiacia /(i>')iesiaita, for example) just as readily as it will feed upon 

 the juicy Claytonia. 



It is at all events worth noticing that it is just in the hot, more or less arid 

 and de-sert parts where animals are least numerous, that both the spinj' and tlie 

 especially succulent plants are best developed, and it seems reasonal)le to connect 

 this with their climatic rather than with their animal environment. 



After crossing the Macundja our course lay northwards along the valley of the 

 Stevenson, the Macumba River being formed l)y the union of the Stevenson 

 coming down from the north, and the Alberga which runs in fi-om the east, having 

 its principal source probably in the Musgrave Range. As usual the river was 

 simply a sandy bed with a few water-holes at intervals. 



Our camp for tiie night was pitched when possiijle by the side of a water-hole. 

 These are all very much like one another. A patch of green scrul) lines their 



