Miscellanea us. 147 



glanduliferous hairs which cover the surface of the leaf, settles upon 

 it, the hairs stiflFea and curve towards those of the opposite side, so 

 as to form a sort of uet under which the little creature remains im- 

 prisoned. It is certain that we often find one or more insects 

 struggling or dead under the hairs of this leaf, and this, I helieve, is 

 the best proof that we possess of the excitability and movements of 

 the hairs in Drosera. I think however that these hairs are not ex- 

 citable, and that they are incapable of performing the movements 

 attributed to them. I have often endeavoured to irritate them, but 

 have never succeeded in observing anything which would indicate the 

 L^ast degree of excitability, although I have been placed in circum- 

 stances very favourable for these experiments ; for after a recent shift- 

 ing of the Orchideous plants at the Museum, a great many specimens 

 of Drosera grew up amongst the Sjihaynum emploved in this ope- 

 ration, and there were for a long period leaves of all ages in the con- 

 servatory, so that I was enabled to experiment upon organs at differ- 

 ent degrees of development. Nevertheless, I never perceived the 

 least inflexion which was not occasioned by the pressure which I 

 employed. 



It ajjpears to me that the following is the cause of the capture of 

 insects by the leaves of Drosera. During their development these 

 leaves are rolled in upon themselves, the margins of the limb are 

 curved towards the centre, and the hairs have the same direction. 

 In growing, the limb spreads by degrees and the hairs also stiffen 

 successively from the circumference to the centre. If, before the 

 whole of the hairs have become stiff, some insect comes to suck the 

 viscous juice which exudes from their glands, it presses into the 

 space which they leave between them at the centre of the leaf, and 

 becomes entangled in the mucosity. The growth ol the leaf con- 

 tinues nevertheless, the incurved hairs are straightened one after the 

 other, but the unfortunate insect dies before they become quite 

 straight. 



The glauds which secrete the viscous matter above mentioned are 

 deserving of the attention of botanists from their interesting struc- 

 ture, which has not \ et been sufficiently studied. ]\ieyen gives the 

 most detailed description of them in his memoir ' Ueber die Secretions- 

 Organe der Pflanzen ;' but this description, although apparently mi- 

 nute, is notwithstanding very incomplete. It may be resumed as 

 follows : — " The glands of Drosera are elliptical and pedicellate ; a 

 spiral vessel runs up the pedicel and penetrates into the gland." 

 Meyen adds in his ' Physiology' (p. 47f<), that the gland, like the 

 pedicel, co'.isists of a very compact cellular tissue. Let us now see 

 whether this is the structure of the secreting organs. We shall soon 

 see that the form of the glands of the margin of the leaf of Drosera 

 rotundifolia has not even been indicated. In fact Meyen has only 

 described the elliptical pedicellated glands, and yet he speaks of mar- 

 ginal and central glands ; but he only distinguishes their inequality 

 of size : he has seen only that they are longer than the others, but 

 has not noticed that their organization is d'fferent. 



10* 



