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LEUCOBRYUM GLAUCUM SCHP. 
By W. H. Burrell, F.L.S. 
Leucobryum glaucum Schp. , in unattached double convex discs, has 
recently been detected in Norfolk, England, enabling me to take an active 
interest in the two previous records, published in Dixon’s “Handbook of 
British Mosses,” and in The Bryologist, Vol. IX, No. 4, July, 1906. The 
former describes spheroidal balls or cushions from Hedsor, Bucks, entirely 
unattached, consisting of stems radiating outwards from a central point. 
The latter refers to an apparently similiar cushion found by B. D. Gilbert 
in hemlock woods in Otsego Co., New York, which was observed to be rest- 
ing in a matrix, of its own diameter, and about half an inch deep. Mr. Gil- 
bert offers no explanation as to how the cushion separated itself and 
developed its radiate growth, neither does he state what the underlying cup 
was composed of; if it consisted of the older portions of Leucobryum stems, 
from which the cushion had separated, there is no analogy between the 
Otsego and Norfolk examples; if, however, the cup was composed of earthy 
matter, similar causes may have originated the cushions, heavy rain or flood 
causing it in this instance to become embedded. 
A careful study of the large quantity of material at hand leads me to 
expect this form of Leucobryum to be wide spread and frequent; it is with 
the object of stimulating observation that this note is prepared. 
In the parish of Aylmerton, Norfolk, on the slope of a hill, under the 
shade of beech trees, several hundreds of small cushions of Leucobryum are 
growing, a series of intermediates showing the connection between normal 
plano-convex tufts firmly attached to the forest soil and double convex unat- 
tached discs exhibiting no distinction between base and summit. Some are 
resting on fallen leaves of the previous autumn to which they are attached 
by radicals and mycelium ; others are resting on their convex surface with 
the plane earth-covered base directed skyward through inversion: one fine 
tuft four inches (10 cm.) in diameter, with a clean base devoid of earthy mat- 
ter was resting on a bed of Mnium hornum L. : it had been there long enough 
for the base to conform to the inequalities of the underlying moss and the lat- 
ter was slightly discolored ; others had in varying degrees pushed out new 
growth, illustrating stage by stage the gradual formation of the double con- 
vex cushion. Perfect cushions are the exception, rather than the rule, though 
many occur. 
The rigid habit of the plant, its method of vegetative reproduction and 
the structure of the leaves are important factors in the development of the 
Explanation Plate XII. Leucobryum glaucum Schimp. 
Fig. 1. Portion of leaf with bud developing from rhizoids X 15 diam. 
Fig. 2. Transverse section of portion of leaf showing a single layer of 
chlorophyllose cells (a) embedded in 2-4 layers of hyaline cells 
with bordered pores (b) X 170 diam. 
Figs. 3, 5, 7. Cushions, lower surface, reduced to one-half diam. 
Figs. 4, 6. Cushions, upper surface, reduced to one-half diam. 
