612 



externally with prominent transverse bars. The texture of the leaves 

 and of the capsule is more dense and ojjaque, and the perichsetial leaves 

 and vaginula are considerably longer than in D. adiantoides. In a 

 diied state also the two mosses have a different aspect, the foliage of 

 D. taxifolium being less disposed to curl. I have never observed any 

 such ambiguities as those vrhich are pointed out by Mr. Sidebotham, 

 (Phytol.581).— fF. Wilson; Orforcl Mount, Warrington, May 5, 1843. 



304. Dicratmm osmundioides and hryoides. The difference existing 

 between these two species was long ago indicated by Meyrin, but his 

 observations have been overlooked. The former of these two mosses 

 has the calyptra mitriform, with the margin at the base inflexed. In 

 D. bryoides the calyptra is constantly dimidiate, and the leaf has a 

 colourless cartilaginous border ; characters which would be amply 

 sufficient to distinguish the two species, even if their mutual resem- 

 blance were greater than it is. They differ also in the form of the 

 capsule, and in the shape of the leaves. I may here remark that the 

 blending of these two species, in ' Muscologia Britannica,' is solely 

 attributable to their not having been compared together with due de- 

 liberation. Some species, in order to be properly understood, must 

 be patiently studied in a living state, and at various stages of growth. 

 If such a method be observed, the student will have no difficulty in 

 persuading himself of the validity of those distinctions by which 

 Polytrichum commune is separated from P. gracile, P. aloides from 

 P. nanum, and Orthotrichum Rogeri from O. affine.— Id. 



305. Calla ^thiopica, L. One evening in April my attention was 

 forcibly drawn to this plant (then in the parlour, not covered by glass), 

 as it was copiously distilling water from the tips of its leaves. The 

 evening gave no signs of an atmosphere overcharged with moisture, 

 and at night the stars shone with brilliance. The roots of the plant 

 had been well supplied with water in the forenoon. Mr. Quekett's 

 admirable paper (Phytol. 218) recurred to mind, and I was induced 

 to examine closely a phenomenon which presented itself to my no- 

 tice for the first time, and in circumstances where I could not expect 

 to see it. The exudation was observed on such leaves only as had 

 the upper portion of the cylindrical points faded and discoloured, 

 the line of demarcation between the faded and the living part indi- 

 cating the spot where the fluid escaped ; in every other respect the 

 position of the outlet was altogether indeterminate, some leaves dis- 

 charging their fluid at the base of the cylindrical point, others at a 

 spot still lower down, and one at a considerable distance from the 

 top, but close to the margin of the leaf, at a part which had become 



