ants' nests. 495 



vation of tbe reception of the food by tlie ants is as yet wanting liere. 

 The Acacias which are free from ants do uot possess these ])eculiar 

 arrangements. 



(b) Imperfect symbiosis. — Belt has ascertained that the species of 

 Fseudomyrma which inhabit Acacia thorns are fierce, warlike creatures, 

 and keep every foe at a distance from the phint, including the leaf- 

 cutting Atta, the forest destroyers of America. The adaptation of the 

 ant to the plant is ascertained as soon as it is proved that the respective 

 species always lives and can thrive only in the corresponding plant. 

 This has recently been sufticiently demonstrated iu the case of Psendo- 

 myrma Jlavidula and PseiuJomyrma. helti. With all this, however, it is 

 not yet proved that all Acacias inhabited by ants coutribute anything 

 on their ]>art to this arrangement. In fact, this is not yet i)roved in 

 the case of many species; in others, it is very doubtful or imju^obable, 

 because, on the one hand, there are many hollow Acacia thorns without 

 ants (Mr. Wroughton has sent me such from India), and because, on 

 the other hand, many species of ants of the genera rseuclomyrma, tSima, 

 and Crcmastogaster frequently inhabit these thorns, and frequently 

 make their nests in some other way. These hollow thorns with the 

 round aperture, which the ants make use of, and which are very similar 

 in ai)pearance to that of the gall in tig. 1, have been often depicted 

 and we do not, therefore, think it worth while to rei)roduce them here. 

 I found a thorn of Acacia fistula, which had been brought from Somali 

 Land by Prof. C. Keller, and which was inhabited by Crcmastogaster 

 chiarinii EMERY, divided inside by pasteboard into a few snuill cham- 

 bers. In the case of Cremastogaster chiarinii Em., G. acacia Forel, 

 and C. ruspoUus FoREL, there appears to be an adaptation of the 

 ant to the plant. 



We must now speak of the celebrated pseudobulbs of the epiphytic 

 plants of the genera Myrmecodia and Hydnophytum of the Sunda 

 Islands. Fig. II represents, in half the natural size, the ijhotographed 

 cross section of Hydnophytum montanum, which, with other magnificent 

 specimens of this plant and of its relative, ^fynnecodia, which has 

 often been sketched, was sent to me recently from Java through the 

 kindness of my friend and colleague. Dr. Ad, Frick, of Zurich. The 

 enormous bulb of this plant, which lives as a parasite upon trees, is 

 always pierced by a hollow labyrinth, as represented by the cross sec- 

 tion in our figure. Now, this hollow labyrinth, according to the obser- 

 vations of Forbes, Beccari, Treub, and others, as well as that of 

 Myrmecodia, is always inhabited by ants, which issue from little open- 

 ings near the point of departure of the roots and fiercely attack every 

 one who approaches, so that the natives are very unwilling to fetch 

 these plants. Three species of ants, Iridomyrmex cordatus Smith, 

 Cremastogaster deformis Sm., and Phodole jarana Mayr, were found 

 in Myrmecodia and in Hydnophytum. While, however, Iridomyrmex 

 seems to make its appearance always iu these plants only, Pheidole 



