Chapter X —163— Drosera 



result is not to be doubted, that in all essential points the fed plants 

 forge ahead of the unfed"; Busgen: "We must therefore take it 

 as proven that animal stuflfs are transferred to the plant and that 

 they are of great significance to it for its development, namely, for 

 the development of its fruit, etc."; and finally Francis Darwin 

 said: "These results show clearly that insectivorous plants derive 

 great advantage from animal food." 



Just previously to the publications of Kellermann and v. 

 Raumer's work Pfeffer (1877) had grown Drosera rotundifolia plants 

 from winter buds under cover to prevent the access of insects, and 

 observed that they grew vigorously, evidently leading to the conclu- 

 sion that the carnivory is not always a necessity. Regel (1879) went 

 further than this, claiming that the carnivorous habit is a distinct dis- 

 advantage because he observed that the leaves {Drosera filiformis) 

 were often injured by feeding, and that fed leaves die sooner than 

 unfed ones. It is, however, well known, as Goebel pointed out, 

 that overfeeding often causes decay of the leaf; and to deplore the 

 earlier passing of fed, not overfed, leaves is to ignore the possible 

 good which may have accrued to the plant in the meantime. And 

 Haberlandt was of the opinion, based on field observations in Java, 

 that Nepenthes pitchers appeared to have but a meagre booty, that 

 insectivory is a sort of semi-superfluous, luxus adaptation. In this 

 Massart {through Haberlandt), having had similar field experiences, 

 agreed. Nor did Goebel regard the role of insectivory in the struggle 

 for existence very seriously — it is useful, he said, but not obligatory, 

 and the plant does not meet much competition in its natural habitat. 

 Such more or less contrary views have in the long run been brought 

 to a focus in the idea now generally accepted that carnivory is a very 

 striking and useful adaptation, which, though not always obHgatory, 

 can under circumstances better the condition of the plant. Ad- 

 ditional questions, no less important, however, arose. It will be 

 noted that the above researches were overshadowed by the sole idea 

 of animal food, as supplying chiefly proteids, and this has crept into 

 the textbooks as the dominant thought. Stahl, in 1900, published 

 a long dissertation on the significance of mycorrhizal arrangements 

 in plants, in which he instituted comparisons between those plants 

 with the carnivorous plants, all of which grew in sterile soils. Sar- 

 racenia had been shown by MacDougal (1899) to be free of mycor- 

 rhiza, nor had it been found otherwise in Pinguicula (Schlicht, 1889, 

 through Stahl), Drosera, or Nepenthes (Janse, 1896, through Stahl) 

 and this is now known to be the case for all carnivores. As com- 

 pared with true parasites, mycorrhizal plants and autotrophic plants 

 with very extensive roots, those plants which avail themselves of capil- 

 lary water and in which many forms of animal life perish and are 

 entangled in the foHage {e.g. mosses), and carnivores have poor roots 

 and therefore httle means for obtaining the materials of the soil^ no- 

 tably lacking in salts, especially those of phosphorus and potassium, 

 in which they grow. And while it may be true that it may be shown 

 by experiment that carnivores may obtain all their requirements 

 through their roots, if plentifully supphed to the substrate, this does 

 not show that in a state of nature their arrangements for obtaining 



