CYCLOSIS IN AN'ACHARIS, ETC. 393 



Object-glass being here preferable to the l-4th, and the assistance 

 of the Achromatic Condenser being desirable. With this amplifi- 

 cation, the phenomenon may be best studied in the single layer of 

 marginal cells ; although, when a lower power is used, it is most 

 evident in the elongated cells forming the central portion of the 

 leaf. The number of Chlorophyll -granules in each cell varies from 

 three or four to upwards of fifty ; they are somewhat irregular in 

 shape, some being nearly circular flattened disks, whilst others are 

 oval ; and they are usually from l-3000th to l-5000th of an inch 

 in diameter. "When the rotation is active, the greater number of 

 these granules travel round the margin of the cells, a few, however, 

 remaining fixed in the centre ; their rate of movement, though only 

 l-40th of an inch per minute, being sufficient to carry them several 

 times round the cell within that period. As in the case of the 

 Vallisneria, the motion may frequently be observed to take place 

 in opposite directions in contiguous cells. The thickness of the 

 layer of Protoplasm in which the granules are carried round is 

 estimated by Mr. Wenham at no more than 1-20, 000th of an inch. 

 A peculiar undulating appearance is seen in this, under certain 

 modes of illumination, which suggests the idea of Ciliary action; 

 but this appearance is decidedly affirmed by Mr. "Wenham to be 

 an optical illusion.*' — It is affirmed by Dr. Branson + that the elon- 

 gated cells along the margin of the leaf and forming the midrib 

 contain a large quantity of silex ; the evidence of this being fur- 

 nished by the effect of Polarized light, especially after the leaf has 

 been boiled for a few minutes in equal parts of nitric acid and 

 water, which removes part of the Organic substance, and thus 

 renders the Siliceous portion more distinct, without destroying the 

 form of the leaf. But the observations of Prof. Bailey upon the 

 parallel case of the Equisetum (§ 281) throw a doubt on the vali- 

 dity of this conclusion. 



289. The phenomenon of Cyclosis, however, is by no means 

 restricted to submerged Plants ; for it has been witnessed by 

 numerous observers in so great a variety of other species, that it 

 may fairly be presumed to be universal. It is especially observ- 

 able in the Hairs of the Epidermic surface ; and according to Mr. 

 Wenham, + who has given much attention to this subject, "the 

 difficulty is to find the exceptions, for hairs taken alike from the 

 loftiest Elm of the forest to the humblest weed that we trample 

 beneath our feet, plainly exhibit this circulation." Such Hairs 

 are furnished by various parts of Plants ; and what is chiefly 



* Op. dt., Vol. ii., 1854, p. 131. 



t See Dr. Branson, in "Quart. Journ. of Microsc. Science," Vol. iii. 

 (1855), p. 274 ; and Mr. Wenham, in the same, Vol. iii. p. 277. 



X 'On the Sap-Circulation in Plants,' in "Quart. Journ. of Microsc. 

 Science," Vol. iv. (1856'!, p. 44.— It is unfortunate that Mr. Wenham 

 should have used the term 'Circulation' to designate this phenomenon, 

 which has nothing in common with that movement of nutritive fluid 

 through tubes or channels to which the term is properly applicable ; 

 whilst the term ' Sap ' cannot be appropriately applied to the contents of 

 the individual Cell. 



