444 BIOLOGIC RELATIONS BETWEEN PLANTS AND ANTS. 



this in another way : The plantlets of Myrmecodia, without the help of 

 ants, might, indeed, by reason of their hereditary tendencies, com- 

 mence to form the tubercle but would be unable to develop to adult 

 dimensions. 



The intervention of ants must, then, be considered as indispensable to 

 the life of the plant, since they contribute to the development of the 

 organ that serves as a water reservoir. Were there no ants there 

 would be no internal reserve of water, and the plant would be exposed 

 to all the dangers of drought. It may be remarked here that, accord- 

 ing to recent researches, a similar service is rendered to plants that 

 grow in the sand of Sahara by nematode worms, that act on their sub- 

 terranean organs. These worms (Uterodera, noted for their ravages 

 on certain garden vegetables, particularly the betterave) cause a devel- 

 opment of histological elements adapted to serve as water reservoirs. 



The biologic relations of the ants with the Myrmecodias seem, then, to 

 be symbiotic. The symbiosis is not, perhaps, as close as some think, 

 but it seems difficult to deny its existence. There seems to be good 

 reason to suppose that if, during several generations, the ants should 

 cease to visit the tubercles, those bodies would undergo a progressive 

 atrophy, or at least be reduced to the state of solid tubercles without 

 internal cavities, such as those of Pentapterygium ( Vaccinium) serpens, 

 for example. 



The lodging organs of several myrmecophilous orchids have a great 

 resemblance to those of the Bubiacese we have just been studying. 

 We know among the orchids three examples of which there can be but 

 little doubt. One of these has been known for quite a long time, hav- 

 ing been already mentioned by Eumphius. It is that of an epiphytous 

 orchid, GrammatophyUum speciosum, whose pseudobulb thickens, even 

 after the fall of the first leaves, and within whose fibrous mass ants 

 establish themselves. 



The Lecanopteris deparioides (a fern) has a rhizome similar to the 

 tubercles of Myrmecodia and Hydnophytum, and which, like them, forms 

 a true ants' nest. Within this rhizome there are hollowed-out cavities 

 and galleries that are at first filled with a flocculent matter, analogous, 

 doubtless, to that of the Bubiacese above cited. The ants penetrate 

 the interior of this rhizome by an opening situated on the upper pro- 

 jecting part, upon which the fronds are inserted. The same arrange- 

 ment is found in P. sinuosum, on the surface of whose rhizome are 

 found circular openings, indeterminate as to situation, that seem 

 undoubtedly to be the work of an ant {Iridomyrmex cordata), the same 

 that inhabits Hydnophytum petiolatum. 



Certain Melastomace* are likewise epiphytic and myrmecophilous. 

 Such are the Pachycentrias, epiphytic or pseudo parasitic plants, whose 

 branches, interlacing on the surface of tree trunks, give out a great 

 number of adventitious roots. Upon these roots enlargements are 

 found irregularly spherical in shape; and if, as frequently happens, sev- 



