(150) 



Botany. — "On the harmful consequences of the secretion of sugar 

 lüith some myrmecophilous plants." By Mrs. M. Nieuwenhuis- 

 voN ÜEXKÜLL-GüLDENBAND. Ph. D. (Comiiiunicated by Prof. 

 J. W. Moll). 



(Communicated in the meeting of June 30, 1906). 



During my residence of about eight months at Buitenzorg in 1901 

 I occupied myself chiefly with an investigation of the structure and 

 peculiarities of the sugar-secreting myrmecophilous plants. The results 

 of these observations, extending over some 70 plants, are inconsistent 

 with the opinion expressed by Delpino, Kerner, Trelease, Burck 

 and many others, that the extrafloral secretion of sugar by plants 

 would serve to attract ants which in return would protect the plants 

 against various harmful animals. 



For I was unable to observe in a single instance that the secretion 

 of sugar is useful to the plant; on the other hand it appeared to 

 me that the ants feed on the sugar, but that, instead of being useful 

 at the same time, they injure the plant indirectly by introducing 

 and rearing lice; moreover the extrafloral nectaries attract. not only 

 ants but also numbers of beetles, bugs, larvae, etc. and these are 

 not content with the sugar alone, but at the same time eat the 

 nectaries themselves and often consume the leaves and flowers to no 

 small extent. 



In about one third of the plants, investigated with this purpose, 

 the secretion of sugar in this way certainly does much harm ; with 

 another third the plants experience only little harm by attracting 

 the undesirable visitors, while with the last third no indication at 

 all could be found that by secreting sugar they were worse off than 

 other plants. 



Of those that were indirectly injured by secreting sugar I here 

 only mention a few examples out of the many which I shall consider 

 more extensively elsewhere. 



Spathoglottis plicata Bl. is a common orchid in the Indian archi- 

 pelago. In the environs of Buitenzorg it is e.g. found on the Salak, 

 and it is used in the Botanical Garden to set off" the beds in the 

 orchid quarter. Its leaves (all basal leaves) have a length of as much 

 as 1.20 M., according to Smith, they are narrow, have a long point 

 and are folded lengthwise; their inflorescence is erect, reaches a 

 height of about 2 metres and bears at its extremity, in the axils 

 of coloured bracts, a number of flowers, the colour of which varies 

 from red violet to white. The bracts and perianth leaves have blunt, 



