Oct., 1894. ON THE DISPERSAL OF THE NUTLETS. 285 



being protected from wet, which is a possible end for such an adap- 

 tation. 



Lastly come those cases of [somewhat rare occurrence, in which 

 the capsule or calyx, as the case may be, opens in damp air and 

 shuts up when dried. These movements, with which others are co- 

 ordinated, form the subject of the present paper. How far they are 

 of biological importance to the plant it is not at present possible to 

 say. It is only by the collection of a large number of instances that 

 we can hope to arrive at a conclusion. 



Hygroscopic movements, apparently adapted for the dispersal of 

 seeds in wet weather, are confined chiefly, although not by any means 

 entirely, to plants indigenous to countries having long periods of 

 drought, during which the seeds, if dispersed, would have little chance 

 of germinating. 



Familiar instances of this phenomenon are found in the Crucifer, 

 Anastatica hierochuntina (Rose of Jericho) and the Composite, Asteriscus 

 pygmcBiis (Coss et Dur), both of which are inhabitants of deserts. 



In 1878 Steinbrinck (2) drew attention to the fact that the 

 capsules of two species of Veronica open more widely when sprinkled 

 with water, and in 1883 he gave an account (6) of a similar movement 

 in the capsules of Caltha palustris and several species of Mesembrian- 

 themum and of Veronica. This was found by MacLeod (7) to hold 

 true of Veronica arvensis and V. serpyllifolia. Volkens (8) and Schinz 

 (9) have described other cases of hygroscopic movements of a like 

 character. 



Verschaffelt (10) has described the striking instances of Salvia 

 horminum, Brunella vulgaris, B . grandiflor a, SLudlberis nmbellatuni. Finallyy 

 Ascherson (11) has given to these movements the name of hygro- 

 chasia ; and, after reviewing critically the literature on the subject, 

 he describes two new cases, Lepidium spinosum and Amnii Visnaga. 



On examining about forty Labiates in fruit I have found fourteen 

 species which show hygroscopic movements. Of these there are 

 eleven species which move in such a way as apparently to favour 

 the dispersal of their nuts in wet weather. 



The method of observation was in each case as follows. The 

 plant in the dry condition was drawn to scale. Water was then 

 sprinkled on it, and when the consequent movements had taken 

 place, a drawing was again made. In order to observe the more 

 minute movements of the calyx-teeth, a single calyx was pinned 

 down to a cork, under a microscope furnished with an eye-piece 

 micrometer, and the change in the position of the teeth noted, when 

 the calyx was wetted. 



The movements may be classified in the following way : — 



I. — The movements closely resemble those ot Brunella vulgaris^ 

 described by Verschaffelt (10). 



The axis of the calyx is turned upwards so as to be almost 

 vertical (the mouth being up), and the opening is more or less com- 



