THE INKER LIFE OF PLANTS 327 



habits which prove how closely the modification of their lives has 

 affected their race and species. If we select the case of the ivy, for 

 example, we note a weak-stemmed plant, developing on that stem 

 clusters of small root-like processes, which, like the "hold-fasts'"' of 

 the gardener, serve to attach it to the wall over which it may extend 

 its growth, or to the tree on which it climbs. But the nourishment of 

 the ivy, like that of ordinary plants, is a matter of ordinary root and 

 leaf function. With leaves of its own, it can inhale and decompose its 

 aerial food, and by means of its root it can absorb from the ground 

 the food-materials which the soil supplies. 



Let us now imagine the case of a plant in the ivy shape, with 

 its false "roots" adhering to another plant, and which becomes 

 accustomed to utilise these "roots" for nourishment. It is not 

 difficult to conceive of such roots, at first used for fixation alone, 

 becoming adapted for nutrition also. If we suppose that these 

 " roots," penetrating the tissues of a tree, acquired a habit of 

 absorbing nourishment in the shape of the tree's sap, we should thus 

 outline the preliminary stage in the development of a more typical 

 parasitic habit. As time progressed, that habit would assert itself 

 with greater force. The absorption of ready-made sap on the part 

 of any plant, is an easier and more satisfying process of nutrition than 

 the work of elaborating sap on its own account. A clear advantage 

 in the " struggle for existence " would thus be gained ; and the 

 effects of a rich and satisfying dietary would be sufficient to induce a 

 further perpetuation and a yet higher development of the parasitic 

 life. From the ivy stage, then, the plant might pass to the mistletoe 

 stage, in which the connection between root and ground has been 

 dissolved, and wherein the plant, whilst retaining its leaves, has 

 become wholly dependent for fixation and lodgment on its neighbour- 

 tree. How powerfully the case of the mistletoe has struck Mr. 

 Darwin as dependent upon a multiplicity of causes, which originate 

 and reside within the inner currents and constitutions of plant-life, may 

 be gathered from his own words. " In the case of the mistletoe," says 

 Mr. Darwin, " which draws its nourishment from certain trees, which 

 has seeds that must be transported by certain birds, and which has 

 flowers with separate sexes absolutely requiring the agency of certain 

 insects to bring pollen from one flower to another, it is equally pre- 

 posterous to account for the structure of this parasite, with its relations 

 to several distinct organic beings, by the effects of external conditions, 

 or of habit, or of the volition of the plant itself." 



The case of the carnivorous plants and of their allies, which have 

 just been- mentioned as illustrative of the peculiar conditions that 

 rule the inner life of plants, may be shown to exhibit an analogous 

 course of development to that which has given us the mistletoe and 

 its neighbours. Developing in another direction, it is true ; and 



