DROSERA ROTUNDI FOLIA. 



[Chap. I. 



The tentacles on the central part of the leaf or disc are short and 

 stand upright, and their pedicels are green. Towards the margin 

 they become longer and longer and more inclined outwards, with 

 their pedicels of a purple colour. Those on the extreme margin 



froject in the same plane with the leaf, or more commonly (see 

 ig 2.) are considerably rettexed. A few tentacles spring from the 

 base of the footstalk or petiole, and these are the longest of all, 



Fig. 2. 



{Drosera rotiindifolia.) 



Old leaf viewed laterally ; enlarged about five times. 



being sometimes nearly i of an inch in length. On a leaf bearing 

 altogether 252 tentacles, the short ones on the disc, having green 

 pedicels, were in number to the longer submarginal and marginal 

 tentacles, having purple pedicels, as nine to sixteen. 



A tentacle consists of a thin, straight, hair-like pedicel, carry- 

 ing a gland on the summit. The pedicel is somewhat flattened, and 

 is formed of several rows of elongated cells, filled with purple fluid 

 or granular matter.' There is, however, a narrow zone close be- 

 neath the glands of the longer tentacles, and a broader zone near 

 their bases, of a green tint. Spiral vessels, accompanied by simple 

 vascular tissue, branch off from the vascular bundles in the blade 

 of the leaf, and run up all the tentacles into the glands. 



Several eminent physiologists have discussed the homological 

 nature of these appendages or tentacles, that is, whether they ought 

 to be considered as hairs (trichomes) or prolongations of the leaf. 

 Nitschke has shown that they include all the elements proper to 

 the blade of a leaf; and the fact of their including vascular tissue 

 was fonnerly thought to prove that they were prolongations of the 

 leaf, but it is now known that vessels sometimes enter true hairs.* 



According to Nitschke (' Bot. 

 Zeltunj?.' 181. p. 224) the purple 

 Hiikl results from the motanntr- 

 phoKls of chlorophyll. Mr. Sorby 

 <>x:iiiiln'<] the coiourlnK mutter 

 with the spectroscope, and In- 

 forms me that It consists of the 

 commonest species of erythro- 

 nhyll, " which Is often met with 

 In leaves with low vitality, nnil 

 In parts, like the petioles, which 

 carry on leaf-functions In a very 

 Imperfect manner. All that can 

 be said, therefore, Is that the 



hairs (or tentacles) are coloured 

 like parts of a leaf which do not 

 fulHI their proper ofBco." 



* Dr. Nitschke has <llscus8e(l 

 tills subject In ' Hot. Zeltung,' 

 isdl. n. 241, &c. 8cc also Dr. 

 WarmniK C Sur la Dlffi^rence 

 entre les Trichomes,' &c., 1873), 

 who jjlves references to various 

 publications. See also Groen- 

 land and Tr^cul, Annal. de 8c. 

 nat. hot.' (4th series), torn. 111. 

 18o5, pp. 297 and 303. 



