98 
AN UNUSUAL PINE. 
ring a visit some time ago to the New York Botanical 
ee while passing through the glass houses in company with 
Professor Britton, my attention was attracted to a curious speci- 
men ofa pine, Pinus pinea. From the illustration of this plant 
(Fig. 24), there are evident two kinds of branches with respect 
to the size and shape of the leaves which they bear, and it is 
frequently other conifers) always bear two kinds of leaves. 
This dimorphism has an interesting bearing on the geological 
history of the genus Pinus and the closely related genus Larix or 
arch, a matter which has been very much discussed by the 
morphologists. 
Turning to the example in our illustration it will be noted that 
the lower branches are studded with short stiff leaves, except in 
a very few places where longer, twisted ones occur. These are 
like those of the upper branches and chief stem, and, as in the 
pines in general, are arranged in groups, or fascicles. Examina- 
tion of the specimen would show that, wherever a fascicle occurs 
on the lower branches, it would, in each case, be found in the axil 
of one of the shorter leaves which occur singly. The explan ation 
is really a very short branch bearing brown, papery sheath- 
scales (which fall away in, e. g., the ad and are persistent in 
the yellow pines), surrounding the basal portions of two, three, 
(occasionally four) or five long, slender green leaves, or ‘‘ needles.’ 
n one species, Pinus monophylia Torr. & Frem., there appears 
to be but one leaf, but by closer examination a vestigial second 
leaf may be found, enclosed within the sheath, the exception 
thus proving the rule. In the case before us, there are three 
needles in the fascicle. It is of significance that Pinus pinea 
and P. monophylla are members of the same sub-section accord- 
ing to Engler & Prantl. 
In all seedling pines the first foliage leaves formed, after the 
cotyledons, are single, so that during its early development, the 
