522 SIR JOHN LUBBOCK ON STIPULES, 
Axillary buds in their early stages are protected by the petiole, 
stipules, and tomentum, except in those cases where they arise 
at nodes after the fall of the leaf. The stipules and a small ele- 
vation at the scar of the petiole then protect them slightly. 
In Mercurialis perennis, Linn., the leaves are opposite, decus- 
sate, ovate or lanceolate-elliptic, petiolate, stipulate, crenate- 
serrate, pubescent, with ascending and slightly incurved nerves. 
The variation in and evolution of the leaves may best be studied 
by an examination of the subterranean resting-buds and of the 
development of the stems with their leaves in spring. 
Three pairs of leaves are reduced to the condition of scales 
without stipules, and there are two other pairs that more properly 
belong to the rootstock or rhizome. The first pair of the flowering 
stem are broadly triangular and slightly connate at the base, 
forming an efficient protection to the bud before growth com- 
mences. By the elongation of the internodes the second and 
third pairs become aerial. Each scar-like leaf is triangular, 
stem-clasping,and separated from its companion by an appreciable 
interval, but connected by a slender ridge across the stem. The 
fourth pair (in the specimen examined) consisted of small but 
perfect, petiolate and stipulate leaves. The stipules are ovate or 
narrowing to subulate and membranous, intrapetiolar, free, but 
touching one another by their contiguous edges, and also touching 
or even underlapping the edge of the petiole. From the point of 
contact of two intrapetiolar stipules a ridge runs down each side 
of the stem to the middle of the petioles of the next pair beneath. 
This applies to all the perfect leaves. The ridges decussate with 
the leaves, so that, although there are four ranks of ridges on the 
stem, they are interrupted on the two sides alternating with the 
sides bearing the stipules. 
The stipules afford comparatively little protection to the ter- 
minal bud, and the stem is unbranched. The leaves are involute 
in vernation from the base nearly to the apex, but a small portion 
is open, giving each a quill-like appearance. Each is separately 
folded, and all attain a considerable size before opening, so that 
they protect the younger members of the bud. 
Judging from the form of the four scale-like pairs of leaves, 
the stipules are derived by separation from their edges. This 
would leave the petioles without sheaths and at the same time 
allow the lamina to become involute at the edges from the base 
upwards. The ridges may perhaps indicate that the leaves 
