CH. VIIl] DROSERA. 207 



After one or two minutes have elapsed to give time for 

 the leaflet to sink, the above process of reading — revers- 

 ing — and reading again must be gone through, when the 

 angular movement will be considerably increased, and 

 may be even double what it was before stimulation. The 

 same specimen should be used to measure the rigidity of 

 the leaflet in the nocturnal position. It w^ill be found 

 that the excursion is very much smaller at night, — some- 

 thing like I of what it is in the day. 



(238) Drosera : stimulated by meat. 



The readiest way to observe the general character of 

 the movement of the tentacles is to place a very minute 

 fragment of raw meat on the gland of one of the outer 

 ones ; this usually causes strong inflection in 7 or 8 

 minutes, by which the meat is after a time carried to the 

 centre of the leaf. The gland should be carefully watched 

 under a lens in order that the time may be noted which 

 elapses between stimulation and the beginning of the 

 movement. An active leaf ought to show distinct move- 

 ment in half-a-minute. In all experiments on Drosera 

 leaves should be selected which have good drops of 

 secretion on the glands, and which show a healthy red 

 colour. Leaves which are too old are of a dark red and 

 should be avoided. 



(239) Drosera : irritated by contact luith inorganic matter. 



The tentacles may also be excited by other substances, 

 e.g. by fragments of pounded glass placed on the glands. 

 It is well to use coloured glass, so that it may be possible 

 to see easily whether the fragments actually touch the 



