14 FUTL'UE 15()TA.MST. 



tatioii. In iMiglaucl, for iiLstaiicc-, we have iiiaiiy anmial«, and in 

 Tripoli and Kgypt there are numerou.s tiny fonn« whose life is 

 confined to the few days during* which the soil is kept moist by a 

 shower of rain. They spring, blossom, and die in perhaps three 

 days. The fact that many of our annuals are porennial at the 

 Cape proves tliat there is no real distinction between the two 

 forms. 



Every tree and slirub, again, has a method of branching 

 peculiar to itself, but ^'arying much according to the particular 

 situation. Tliis depends on which of the possible buds are allowed 

 to develop, and how long each is able to grow before it is checked. 

 Thus, in a very sunny or windy place a twig grows only a 

 very short distance. Its tissue soon becomes so thick that it can- 

 not elongate, though it may become wider ; it therefore stops, and 

 another bud sends out a little twig wliich stops, and yet another, 

 and so or. The result of this is a dense twiggy branclihig wliich 

 one finds typically in plants growing- by the sea or in exposed 

 places. 



Another important effect of the development of the stem isj 

 the rosette type of plant, such as, e.g., the daisy. Here the inter- 

 nodes are suppressed as a result apparently (jf exposure, for many] 

 of these rosette forms will develop internodes if grown iu moist,! 

 half-shaded places. However produced, the rosette shape isj 

 characteiistic of plants that grow on bare earth, and whose leaves 

 can lie flat down upon the soil. The plant gains by this structure, 

 for its cushion or rosette of leaves retains dew, and keeps the earth 

 below moist, while not having- an expansive stem to make, the 

 plant can send a long root into the rock crannies, or use up its sur- 

 plus material in flowering branches or in vivid colour. In this 

 case you see the climate or exposure, by suppressing the internodes, 

 forms a rosette of leaves fiat on the ground, which is a foi'm exactly' 

 suited to the circumstances. 



This is a good example of how plants have a certain structure, 

 and also of how these have been produced. To give a good 

 idea of the present theory of the origin of variations, as I hold 

 it myself, it is necessary to go a step or two further. "We 

 will suppose that a species of an ordinniy kind of Iliei-aciuni, 

 common in glens and corries, has had a seed blown by wind 

 to an exposed rock ledge at some distance off. The exposed 

 situation will have the elTect of suppresshig the internodes so that 



