BIOLOGIC RELATIONS BETWEEN PLANTS AND ANTS. 431 



The Endospermum moluccanum is a myrmecophilous euphorbiaceous 

 plaut known to the oldest authors who have treated of the flora of 

 Malasia. It is the Arbor regis of Rumphius, "cujus truncus intus inhabi- 

 tatur plerumque ea copia forinicarum, ut vix aliquis arboruin proprius, 

 inulto minus caudam altruncare audent." Its native name is caju sum ut, 

 that is, ant tree. 



At the base of the leaves of this tree, where the limbus is inserted 

 on the petiole, are found two nectariferous glandules that, there is 

 every reason to suppose, are capable of attracting ants. It is not yet 

 known whether the branches are hollow or not. Rumphius speaks, it- 

 is true, of openings upon the branches by which the ants pass in and 

 out but it may be that his Arbor regis is rather Hernandia ovigera, a 

 plant that is possibly myrmecophilous, or a related species of Endos- 

 permum of New Guinea {Endospermum formicarum), whose branches 

 are hollow and provided with well-marked perforations. 



One of the most interesting facts in the history of this tree is the 

 following: It seems, according to the observations of Beccari, that it 

 attains in its native forests such proportions as to justify the name 

 Arbor regis, but when it is transported to tropical botanic gardens its 

 height is considerably less. He considers the cause of this dimor- 

 phism to be the absence of ants from the cultivated plants, for he 

 assumes that those insects, by the irritation in the internodes, stimulate 

 growth. The ants, finding upon the Endospermum nectar and lodging, 

 render it a signal service by causing indirectly its development. When 

 the tree has attained, in its natal forest, "royal" dimensions its inflo- 

 rescence overtops the other trees and the fertilization of the plant, 

 which is effected by the wind, is greatly facilitated. Thus, in the most 

 roundabout manner, the ants aid in pollination. This is a most curious 

 example of an anemophilous plant becoming entomophilous, so as to 

 utilize the visits of insects that indirectly aid fertilization. 



The Endospermum formicarum, a species related to the preceding, 

 has branches naturally and constantly enlarged and hollow, but we do 

 not know if the perforations they present are produced by the agency 

 of ants. Their position, which seems constant (in view of the few 

 branches that are turned upward), gives rise to the supposition that 

 this is the case, besides iucomplete perforations are found involving 

 only the bark and the outer fibers of the liber, and these must be the 

 unfinished work of ants. There are also cicatrices which must cor- 

 respond to the orifices commenced by ants and then closed up by the 

 proliferation of the walls. 



What stopped the ants in the work of perforation? The density of 

 the internode, if they attack it at its base, a density that leads them 

 to arrest their work and attack it higher up where the tissue is not so 

 hard. These partially cut holes the plant closes up by cicatricial tissue. 



At the summit of the petiole, near the bifurcation of the large nerv- 

 ures on the lower surface of the leaf, are found glandules that appear 

 to serve as nectaries. 



