Kehniary — Marcli 18S9. 



PSrCHE. 



17 



At about the time when Beecari was 

 making his first observations on these 

 Malayan plants, Belt (2) was en- 

 gaged in a similar study of the bulls- 

 horn Acacia in tropical America, and 

 here, as in the case of extra-nuptial 

 nectar, the credit of having first recog- 

 nized the protective signification of the 

 structure, is shared by Belt and Delpino 

 (6, 91 ). As a result of his studies and 

 those of Francis Darwin (5) and 

 Schimper (27), it seems to be defi- 

 nitely settled that in the spongy enlarged 

 stipular thorns of several species of 

 Acacia^ certain ants find shelter, and 

 are kept upon the plant by a sugarv 

 secretion similar to that which attracts 

 wandering ants to so many other 

 species of this and other genera, while 

 in highlv nutritious bodies at the tips 

 of the leaflets is to be seen a furthei" 

 food.-supply, — the three provisions secur- 

 ing their permanent residence. 



Cecropia peltata and some other spe- 

 cies of the genus are also known, thanks 

 to Fritz Mueller ( 19). Francis Darwin 

 (5), Schimper (27), and others, to 

 produce upon their petioles food-bodies 

 that are likewise eagerly gathered and 

 eaten by ants, which inhabit the 

 hollow stems of these species. Qiiite 

 recently Schimper (27) has shown that 

 in C. adenop7is an unmistakable pro- 

 vision facilitating the entrance of the 

 ants, exists in a thin soft spot obsei"vable 

 on each internode of the hollow stem, — 

 a fact which was indicated in 1876 for 

 the Imbauba, bv Fritz Mueller (4). 



The number of species that may be 

 classed as truly mvrmecophilous, in tliat 



they afibrd lodging, sometimes accom- 

 panied by a provision of nectar or solid 

 food, or both, calculated to maintain 

 upon them a permanent army of ants, 

 is already large. All are, so far as I 

 know, phaenogams, but they are distri- 

 buted through widely separated orders 

 in this group. To Beecari, more than 

 to any other single naturalist, is due the 

 credit of having systematically under- 

 taken their study in the field ; and few 

 biologists have published their observa- 

 tions so svmiptuously as his appear in 

 the volumes of his ''Malesia." Unlike 

 the plants with simple extranuptial nec- 

 tar, these symbiotic plants often show a 

 restriction in the species of ants which 

 frequent them. And it is interesting to 

 observe that closely related species some- 

 times inhabit mvrmecophilous plants of 

 widely separated regions.* Time will 

 not permit me to enter into a more de- 

 tailed discussion of the many cases of 

 proved or probable symbiotic myrmeco- 

 philism, Init enough has been said to 

 show that on the one hand mvrmeco- 

 philous plants join closely to those which 

 provide food for a body-guard of ants 

 which they do not furnish with a resi- 

 dence ; while on the other hand thev 

 ofier equally good transitions to those 

 more or less constantly inhabited bv ants 

 which must seek their food from other 

 sources than special secretions or deriva- 

 tives of the plant. While both of these 

 classes are represented in temperate 

 climates, it is suggestive that the most 

 highly specialized cases of mvrmeco- 

 ])hllism are not known to occur out- 



* Cf. Schumann, /. c, p. 416. 



