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head apex, frequently semilunar above (comparable in form to the section of 
the apical cell of lamellae in Poly trichum commune , but usually asymmetri- 
cal); (cf. Fig. 3a.) These cells are connected with the adjoining cells of the 
next row by only a very narrow attachment, the greater part of their surface 
being free; they are frequently almost without chlorophyll grains above, 
with a dense mass of chlorophyll collected at the extreme base or proximal 
end. 
In addition to this marginal row of cells, the succeeding rows (cf. Figs. 
1, 2), are also frequently extremely turgid, clavate, and so strongly protuber- 
ent at the upper or distal end as to be free from contact with the adjacent 
cells except by a very small proportion of their surface. The structure is 
further complicated by the recurving of the margin, which varies greatly in 
extent in different bracts and in different parts of the same bract. When the 
margin is erect, which is usually the case near the base of the leaf, the 
appearance is as at Fig. 3a; higher up the bract, as it gradually recurves, 
the ventral surface of the protuberant subjacent cells comes more and more 
into view, as at Fig. 3c, d; and when this protuberance becomes strongly 
marked and these adjacent cells are almost free at their apex the appearance 
shown in Figs. 1,2, is caused, giving the appearance of a double frill to the 
bracts. This may be still further enhanced by the margin becoming more 
strongly recurved, and by several rows of subjacent cells exhibiting turges- 
cence and protuberance, though it is never so markedly presented by these as 
by the first and second marginal rows. 
This structure is somewhat elucidated by cutting transverse sections of 
the bract. Figs. 4, 5, 6 illustrate various points on different bracts, with 
differing degrees of recurving of the margin. The letters a, b, c, d, in Fig. 4, 
correspond to the positions of the equivalent lettering in Fig. 3, the sections 
being taken at these points (or at least at corresponding points, since the 
sections were not all actually made from the same bract). 
Figs. 5, 6, show the remarkable degree of recurving sometimes attained, 
so that the marginal cell is at times in close contact with three or even more 
rows of cells, and appears to be and probably is adherent to their cell-walls, 
as is often the case in species of Grimmia and Barbula , where the closely 
recurved margin of the lower part of the leaf gradually becomes transformed 
into the bi-stratose thickened margin of the apical part. 
The question naturally arises as to what is the genesis of this remark- 
able, perhaps unique formation. Is it an adaptation to a special environ- 
ment, or a reversion to an ancestral type, or is it a merely fortuitous sport 
due to abnormal conditions of growth ? I am not able to give any satisfac- 
tory reply: I can only suggest one or two ideas which have occurred to me, 
and perhaps some reader will be able to frame an explanation. 
There can be but little doubt that the primary end attained by this 
abnormal cell development is the storage of an increased quantity of water 
or at any rate moisture, an end attained to some extent also by thecapillary 
attraction of the recurved margin. The resemblance of some of the turgid 
marginal cells to the “ flask-cells” of the cortical stem-layer in Sphagna , e.g. 
S. molluscum, at once strikes the eye, and the group of cells looked upon 
