— iog — 
form under discussion. The leaves of most mosses are built up of a single 
layer of cells which quickly part with their moisture in dry air and as readily 
re-absorb it from damp air. The leaves of Leucobryum, however, have a 
remarkable cell structure allied to that of Sphagnum, consisting of a single 
layer of chlorophyllose cells (Fig. 2a) embedded in 2-8 layers of empty hya- 
line cells whose adjoining walls are perforated with bordered pores (Fig. 
2b). When the hyaline cells are filled with water the green color of the 
embedded chlorophyllose cells is seen: when water is displaced by air the 
plant assumes a dirty white color suggestive of the name leucobryum — white 
moss. The water held by these cells after rainfall can be squeezed out as 
from a sponge and renders unattached tufts self-sustaining on the same prin- 
ciple that camels can exist for considerable periods in arid deserts— they 
carry their own supply. In Braithwaite’s British Moss Flora reference is 
made to the abnormal vitality of the genus, and persistent growth even in 
the drying press; dipping in boiling water before pressing is recommended 
to prevent dehiscence of the capsule. 
Leucobryum is not a frequent fruiter: in compensation for the rarity of 
spore formation new growth proceeds from buds developed from radicals 
which are freely formed on the surface of the leaves. (Fig. 1). Regardless 
of the position of the parent tuft these buds develop geotropically at which- 
ever surface happens to be uppermost at the time. The double convex form 
assumed by the most perfect tufts, and to which all conform more or less, is 
favored by the rigid habit of the plant and by its squat growth in the local- 
ity referred to. In its most luxuriant form Leucobryum is a denizen of 
swamps where it forms large bosses 6-8 inches high, but at Aylmerton the 
average height is 1 ^ inches (3-q cm.). A tuft torn from a deep boss, would 
lie prostate: but the short tuft when disturbed has a tendency to come to rest 
either in its normal position or completely inverted, alternating growth 
taking place in two definite directions: too much stress must not be laid on 
this because many examples occur of single stems lying prostrate and pro- 
ducing plano-convex cushions half an inch (12 mm.) in diameter, by the devel- 
opment of buds from the apical leaves. Displaced plants do not to any great 
extent appear to recover an erect position by curvature of the stem; they 
remain in the position accident assigns them and form a frame work to 
which the new growth from buds conforms. 
Assuming that I am correct in attributing the unattached state to acci- 
dental and repeated disturbance, which brings into play the natural vitality 
of the plant, and stimulates bud formation, it is not difficult to suggest a 
cause for the disturbance. The tread of woodmen and sportsmen and the 
removal of timber play their part, but in well stocked game preserves I have 
long been familiar with displaced moss, especially Dicranum scoparium 
Hedw., and I have attributed this to the scrapping of pheasants. In open 
moorland, where Dicranium forms dense masses, the ground is often lit- 
tered with small tufts which apparently depend upon chance conveyance to 
a congenial spot for continued existence. In woodland, similar displace- 
ment takes place with a slightly different result; in the cool shade Dicranum 
