Chap. XIL DEOSEKA BINATA. 283 



of ammonia to 218 of water (1 gr. to 2 oz.), and in 5 m. they 

 were all so much darkened as to be almost black, with their 

 contents aggregated. They do not, as far as I could observe, 

 secrete spontaneously; but in between 2 and 3 hrs. after a 

 leaf had been rubbed with a bit of raw meat moistened with 

 saliva, they seemed to be secreting freely ; and this conclusion 

 was afterwards supported by other appearances. They are, 

 therefore, homologous with the sessile glands hereafter to be 

 described on the leaves of Dion sea and Drosophyllum. In 

 this latter genus they are associated, as in the present case, with 

 glands which secrete spontaneously, that is, without being 

 excited. 



Drosera bhiata presents another and more remarkable pecu- 

 liarity, namely, the presence of a few tentacles on the backs of 

 the leaves, near their margins. These are perfect in structure ; 

 spiral vessels run up their pedicels; their glands are sur- 

 rounded by drops of viscid secretion, and they have the power of 

 absorbing. This latter fact was shown by the glands imme- 

 diately becoming black, and the protoplasm aggregated, when 

 a leaf was placed in a little solution of one part of carbonate 

 of^ ammonia to 437 of water. These dorsal tentacles are short, 

 not being nearly so long as the marginal ones on the upper 

 surface ; some of them are so short as almost to graduate into 

 the minute sessile glands. Their presence, number, 'and size, 

 vary on different leaves, and they are arranged rather irre- 

 gularly. On the back of one leaf I counted as many as twenty- 

 one along one side. 



These dorsal tentacles differ in one important respect from 

 those on the upper surface, namely, in not possessing any power 

 of movement, in whatever manner they may be stimulated. Thus, 

 portions of four leaves were placed at different times in solutions 

 of carbonate of ammonia (one part to 437 or 218 of water), and 

 all the tentacles on the upper surface soon became closely 

 inflected ; but the dorsal ones did not move, though the leaves 

 were left in the solution for many hours, and though their 

 glands from their blackened colour had obviously absorbed some 

 of the salt. Eather young leaves should be selected for such 

 trials, for the dorsal tentacles, as they grow old and begin to 

 wither, often spontaneously incline towards the middle of the 

 leaf. If these tentacles had possessed the power of movement, 

 they would not have been thus rendered more serviceable to the 

 plant ; for they are not long enough to bend round the margin 

 of the leaf so as to reach an insect caught on the upper surface. 

 Nor would it have been of any use if these tentacles could have 



