78 SCIENCE PROGRESS. 



Dolichos spp., the blue Pentanisia Schweinfurthii, little 

 white Euphorbias, Lasiosiphon spp., etc. These all have 

 the appearance of a flower cut off and planted in the earth, 

 and give rise to remarks on the collector's carelessness in 

 not bringing leaves when worked up by untravelled 

 botanists. With the setting in of the rains, the stems 

 begin to grow and produce leaves until, when the grass has 

 sprung up, all these herbs are in full foliage. This habit is 

 of great advantage to the flowers concerned, as insects 

 can readily perceive the scattered flowers which in the grass 

 would be quite inconspicuous. The same thing occurs in 

 many of the trees. Several species of Dombeya, for example, 

 send out their flowers at this foreshadowing- of the rains 

 and are most conspicuous. 



Another curious effect of the fires is the manner in 

 which trees are either kept down or obliged to protect 

 themselves in some way against their action. In the more 

 arid plains trees seldom exist, or if present occur in the 

 form of stumps perhaps ten years old, but never able to 

 grow higher than a foot or so. Such stumps put out every 

 wet season vigorous shoots, which are annually burnt away 

 and only the short stem with another layer of wood is left 

 to survive. 



Of the trees which do manage to exist in spite of the 

 annual conflagration, the most remarkable are the tree 

 Euphorbias, often twenty to twenty-five feet high. These 

 have angular fleshy branches protected by a leathery 

 epidermis, and besides their milky juice, which contains 

 gum, caoutchouc and other substances, have a large amount 

 of mucilage or slimy matter in the ordinary tissue. This 

 latter is a strongly waterholding substance, and the most 

 violent fire seems unable to do more than scorch a very few 

 of the outermost branches. 



It is a most curious fact that though when living they 

 resist fires in this wonderful manner, dead branches make 

 an excellent fire and blaze up most vigorously. I cannot 

 understand this difference. 



Of the other trees which continue to thrive in these 

 places, there are some seven species which grow in abun- 



