148 COMPENDIUM OF GENERAL BOTANY. 



of Elceagnacece and Myricacece, and finally the well-known root- 

 tubercles of Leguminosce. The latter are neo-formations from the 

 root itself caused l>y and inhabited by fungi (bacteria, rhizobia). The 

 formation of these tubercles can be prevented only by previously 

 sterilizing the soil, for example, at 100 C. moist heat or at higher 

 temperature of dry heat ; from this we conclude that the tubercle - 

 producing organisms are generally distributed in the soil. At 

 certain times, such as near the close of the vegetative period or 

 during lack of moisture, the leguminous plant digests and assimi- 

 lates the greater part of the infecting bacteria, while a small number 

 escape from the decaying tubercles and subsequently enter other 

 roots. 1 



According to the observations of BECCARI, FRITZ MULLER, 

 DELPINO, and A. F. W. SCHIMPER, plants and animals may associ- 

 ate in symbiotic relations. The investigators mentioned made 

 observations on the reciprocal relations between ants and plants in 

 tropical America, communicated by Schimper in 1888. Strictly 

 speaking, this subject does not come within the scope of the present 

 work, yet it has some bearing on true symbiosis, and for that reason 

 will be briefly treated. A certain species of ant lives upon and 

 obtains its food from the branches of a tree (Cecropia]\ in return 

 the ants protect the tree from the injurious and destructive attacks 

 of another species of ant. These " myrmecophilous " trees have 

 a hollow stem transversely divided into chambers; each chamber 

 contains an opening leading to the exterior through which the ants, 

 move in and out. This opening is made by the protecting ants 

 which eat away a thin lateral septum. On the lower surface of 

 the petiole there are small pear-shaped bodies rich in albumen and 

 fatty oil. These drop off very easily, but others are continually 

 formed and serve as food for the protecting ants. 2 



(d) Insectivorous Plants. 



We have seen that plants take up assimilated food, that roots 

 excrete acid for the purpose of dissolving particles of soil ; to these 



1 The literature on this subject is very voluminous. FRANK in his Lelirbuch 

 der Botauik (1893) gives the more important conclusions, also the more important 

 citations, of the literature. 



2 Various myrmecophilous plant-species with different species of protecting ants 

 have also been observed and collected in South America by Dr. H. H. Rusby. 

 TRANS. 



