178 



PSYCHE. 



[February — March 1SS9. 



side the tropics, vviiere, as the obser- 

 vations of Belt, Fritz Mueller, and 

 others show, plants that do not possess 

 some special and eflective means of 

 repulsion or defence are quickly stripped 

 of their foliage, and where, from a per- 

 sistance of this danger since the cooling 

 of higher latitudes, natural selection 

 has been kept in operation after it ceased 

 to work great changes in this respect 

 elsewhere. As might be expected, myr- 

 mecophilism in the moi^e restricted sense 

 may be replaced by other protective 

 devices; and Schimper (27) has in fact 

 shown that a tropical American species 

 of Cecropia is enabled to dispense with 

 the body-guard needed by its relatives, 

 through having very glaucous stems, 

 over which leaf-cutting ants cannot climb 

 to its foliage. 



In 1S87, a rather remarkable paper 

 (16) was published by Lundstrom, 

 of Sweden, in which the hairy nerve- 

 axils on the lower leaf-surface of oaks 

 and other woody plants, the pits simi- 

 larly situated on the coffee plant, etc., 

 and a variety of other structures, were 

 described under the name of domatia 

 (diminutive of SwjAa, a house). The 

 greater number of these are held for 

 mite-domiciles (acaro-domatia) , but it 

 appears as if a fjiirly good series might 

 be made from the simpler acaro-domatia 

 to some of the more specialized pockets 

 of leaves (myrmeco-domatia) inhabited 

 by ants, that have especially been de- 

 scribed by Schumann (28). If this 

 is true, a plausible explanation of the 

 one, when reached, may throw light 

 upon the origin of the other. It may. 



therefore, be worth while to note that 

 Lundstrom holds acaro-domatia for 

 slightly specialized mostly hereditary 

 structures that serve as a shelter for 

 various mites, which benefit the plant 

 by clearing its leaves of fungus spores 

 which may fall upon them, and by con- 

 tributing to their nutrition carbonic acid 

 from their own respiration, as well as 

 their excrement, exuviae, and, idtimate- 

 ly, their dead bodies. While this ex- 

 planation appears far-fetched to most 

 biologists, it is not unlike that applied 

 by Beccari to the myrmecophilism of 

 Myrmecodia., the ant-inhabitants of 

 which are thought to contribute to its 

 nutrition in a similar manner. What- 

 ever the value of his hypothesis may 

 be, it must be conceded that the Swedish 

 botanist has brought together about 

 them a large series of little known and 

 unexplained structures, which can 

 scarcely be looked upon as insignificant 

 by the present school of utilitarian biol- 

 ogists. 



In closing, attention should be called 

 to the relations of ants to the seeds of 

 plants. It is well known that in warm 

 countries some ants carefully and syste- 

 matically harvest the fruit of species 

 which are to their taste, and it would ap- 

 pear that they also take some agricultu- 

 ral interest in the welfare of these plants. 

 While this indicates a high grade of 

 care for the food-producing species, the 

 benefit to the plant is that \vhich a 

 cultivated crop receives from the self- 

 interest of man in its preservation and 

 propagation, without in any way ap- 

 proaching symbiosis. 



