COMMON BRAKES. 
99 
walls, the fronds are smaller, tender, delicate and barren ; the 
margins of the lobes of the pinnules are then flattened, and 
broadly notched. 
Mr. Lees sent me an example of this form, gathered on a wall 
near Worcester cathedral; Mr. Westcombe another, found on a 
wall in the centre of the city of Worcester: it occurs commonly 
on the garden-walls at Deptford; in one instance it has esta- 
blished itself on the brick wall of a house in Union Street, and 
during the present year, 1843, it has made its appearance upon 
the wall which separates the Friends’ burial-ground from Mr. 
Hart’s garden in High Street : Mr. Woodward’s collection con- 
tains a fine example, gathered by Mr. Pamplin, at East Grin- 
stead, in Sussex ; and Mr. Ewing has observed a solitary plant 
for many years growing on the wall of the bridge of the castle-moat, 
Norwich, the fronds varying from three to nine inches in length. 
In these and other instances, too numerous to mention, the same 
characters are always preserved. 
When fertile, the lobes are incurved or convolute at their 
edges, and their elasticity is so invincible, that it is very diffi- 
cult to maintain the lobe in a flat position, 
adapted for an examination of its fructifica- 
tion. The lateral veins, which are placed ei- 
ther opposite or alternately, are twice dichoto- 
mously divided before reaching the margin, 
where they are united together by means of a 
marginal vein. The accompanying diagram 
shows the formula of venation in a lobe which 
has been flattened for the purpose of exhibit- 
ing it more clearly. Attached to the marginal 
vein, a «, and extending throughout its length, 
is a bleached semihyaline membrane, fringed 
with a series of jointed capillary segments. Beneath this mem- 
brane are the capsules, also attached to the marginal vein, and 
arranged along it in a continuous linear series, but more abun- 
dantly at its points of union with the transverse veins. Again, 
beneath this linear series of capsules, is a second bleached and 
fringed membrane very similar to the first. It becomes an inte- 
resting question whether both these membranes can be consi= 
