Notes. 
i 26 
phloem being on the lower or outer side, a position indicative of the 
truly foliar nature of the body in question. 
On the same shoot with these terete leaves are others arranged in 
pairs. The transverse section of either of these twin leaves, whether 
taken in the centre, at the base, or at the apex, shows a nearly semi- 
circular outline, with the convexity beneath, the concavity above. The 
pericycle has the same general shape. In all other material points the 
structure is absolutely the same as in the terete leaves. Sir Joseph 
Hooker therefore examined a section of a ‘connate pair/ and the 
vascular bundle he saw was really double — one portion belonging to 
one leaf, one to the other. My observations as to structure agree 
with those of Bertrand, as illustrated by him 1 , and from them it will be 
seen that (form apart) the structure is in all essentials absolutely the 
same as in the leaves of other species of Pinus. The figure of the 
leaf-structure of Pinus Strobus , given on the same plate by Bertrand 
(fig. 10), shows how closely similar is the leaf-structure in the two 
species. 
Anatomy then shows that the leaf-like body is a true leaf, which 
occurs singly , but occasionally in pairs. There is of course no diffi- 
culty in understanding the latter condition, the anomaly consists in 
the single cylindrical leaf to all appearance occupying the apex of a 
shoot. To clear up this anomaly I investigated the development of 
the constituent parts of the leaf-bud at various stages of growth, and 
without going into details which are for this purpose unnecessary, I 
may say that development supplied the clue which neither outward 
morphology nor internal anatomy sufficed to give. In point of fact, 
in the earliest stages examined there were always two foliar tubercles, 
one of which speedily overpassed the other, so that ultimately all 
traces of the second leaf were obliterated. 
The monophyllous sheath of this pine therefore owes its peculiarity 
to the generally arrested development of one of its two original leaves. 
MAXWELL T. MASTERS, London. 
Loc. cit. tab. ix, figs. 5-6. 
