436 BIOLOGIC RELATIONS BETWEEN PLANTS AND ANTS. 



types in which niyrmecophilous evolution is most advanced the per- 

 foration will become hereditary and the cavity of the lodging organ 

 communicate with the exterior independently of any action on the part 

 of the ants (Clerodendon Jistulosum). 



In all the cases we have reviewed the ants do not seem to have estab- 

 lished themselves in organs whose differentiation relates to the habitat 

 of the host plant. A considerable number of host plants are epiphytes, 

 subject to peculiar physical conditions. They have to especially strug- 

 gle against drought, and a number of them possess in their organs true 

 reservoirs of water. The best known of these myrniecophilous epiphytic 

 plants are the Myrmecodias and the Hydnophytums. We will dwell 

 especially on the former because of the interesting observations that 

 have been made upon them. 



The Myrmecodias and Hydnophytums are epiphytes belonging to the 

 Eubiaceae and attach themselves by means of adventitious roots to the 

 branches of trees, often at a considerable height. These plants are 

 almost wholly formed of large tubercles, globular or cylindric in form, 

 surmounted by one or more leafy stems. These tubercles, which may 

 be either smooth or prickly, enlarge so as to attain several decimeters 

 in diameter. (PL XX.) Instead of forming a solid mass their internal 

 tissue is traversed by a system of intercommunicating cavities and 

 passages that open externally by one or more quite large openings and 

 numerous narrow orifices scattered over the entire surface of the 

 tubercle. 



All those who have collected these strange plants in their natural 

 habitat have found their tubercles inhabited by ants scattered in great 

 numbers throughout the galleries and passages. It was Euraphius, the 

 old explorer of the Malay Archipelago, who first called attention to 

 this. According to him the ants not only inhabit the tubercles, but 

 they produce the entire vegetable. " This is," he says, "a strange crea- 

 tion of nature springing up without father or mother, * * * for it is 

 known that these plants spring from the substance of the nests of ants 

 where there can never have been any seeds, and yet each colony forms 

 a separate plant." Eumphius then distinguishes two kinds of Nidus 

 germinans, according to the species of ants found therein : Nidus ger- 

 minans formicarum rubrarum — that is, a Myrmecodia, and Nidus germi- 

 nans formicarum nigrarum — that is, a Hydnophytum. 



It was Beccari, the eminent explorer of Malasia, who made the first 

 accurate observations upon the biology of these curious Eubiacere and 

 their relations to ants. These observations led him to suppose that 

 the presence of the insects was indespensable to the plant. He thought 

 he had ascertained that at the time of germination the tigellns merely 

 thickens a little at the base and takes on a conical form with the coty- 

 ledons opening at the summit (Fig. 2, Xos. 1-5, PI. XX), thus remaining 

 until a species of ant hollows a little cavity in its side at the most 

 swollen part of the tigellus. If the tigellus is not attacked by the ant 



