242 BOTANY OF THE LIVING PLANT 



tension is released and the walls spring back to their original shape, 

 producing an inrush of water which sweeps the animal into the 

 bladder. There is no escape since the lid cannot open outwards. 

 Death and decay eventually occur and the products are absorbed 



by the plant. 



The extraordinary forms and mechanisms thus seen in carnivorous 

 plants seem to accentuate the importance for them of the gain which 

 follows on this accessory nutrition. Yet all of these plants can live 

 without it, while a surfeit of animal food may be experimentally 

 shown to be harmful to them. These plants stand out as some of 

 the strangest results of special adaptation, and strike the observer 

 as showing a grotesque disproportion between the end gained and 

 the means adopted to secure it. 



Thus many plants, and often those in which we should least expect 

 it, have other methods of nutrition than the autotrophic process. 

 The degree of dependence upon irregular methods varies greatly. 

 The habit is not restricted to any one family or group of plants. 

 It has been seen that sometimes single species or genera, sometimes 

 whole families, are affected. These phenomena are chiefly found 

 in advanced families such as Leguminosae, Orchids, Heaths, or 

 Orobancheae, rather than in those held to be primitive. All these 

 facts taken together lead to the conclusion that irregular nutrition 

 among Flowering Plants is secondary. Its methods have been adopted 

 individually, and comparatively late in Descent, by organisms of 

 which the ancestors were autophytes. Moreover it has not started 

 along any single line of Descent, but along many. In this, as in 

 so many special adaptations, homoplasy, or parallel development, 

 is frequently illustrated. The advance has been along lines of 

 opportunism. Close crowding has encouraged it. Use has been made 

 of such circumstances as offered in order to achieve the end of the 

 plant's existence. That end is not merely the maintenance of the 

 individual, but the propagation of the race by new germs. The case of 

 Rafflesia illustrates this in a striking though extreme manner (Figs. 

 ! 54, 155)- The vegetative system is reduced, in accordance with 

 its parasitism, to the level of fungal hyphae. But its flower is of 

 enormous size, complex in structure, and results in a great output 

 of seeds, each containing a new germ (ovula numerosissima, as 

 Robert Brown called them). The nutritive system, though reduced, 

 is still effective for nourishing this flower. Thus the propagation of 

 the race takes precedence over the vegetative development. This 



