THE MICROSCOPE. 229 
visible with a pocket-lens, and when once seen, then easily apparent 
to the unaided vision. These are characteristic and diagnostic of all 
the leaves on the tree. A suggestive fact is that these cup-shaped 
bodies are found chiefly upon the prominent veins on the lower 
surface of those young leaves, whose hairs are unbranched and 
glandular-tipped, and on the upper surface of those supplied with 
the branching appendages. In the latter, the lower aspect is so 
densely woolly, the branching hairs are so abundant and so crowded 
that no room is left for the development there of the little cups. 
These, apparently as a necessity, have been relegated to the less vil- 
lous upper surface. 
THE OLDER LEAVES OF CATALPA BIGNONIOIDES. 
As the leaves increase in size and age, their upper surface loses 
its supply of sessile, hemispherical glands and, under the pocket- 
lens and to the naked eye, appears entirely smooth, the petioles also 
becoming naked and glossy. The lower aspect, however, becomes 
characteristic. Here the cuticular surface gradually loses its supply of 
simple hairs, which finally entirely disappear from every part, except 
from the margins of the largest and most prominent veins, where they 
are always to be found more or less abundantly. With almost equal 
deliberation there are developed, chiefly in the angles formed by the 
divergence of the larger veins from the midrib below, glandular 
structures which are of diagnostic value in determining the leaves of 
the Catalpa, and which at once differentiate the old or mature foliage 
from that of Paulownia. 
These axillary appendages are fleshy, glandular scales formed 
of colorless or greenish, flattened or hemispherical glands, which 
may at almost all times be seen sitting singly at the margins of the 
midrib and above the glandular mass within the axil below. These 
and the fleshy scales are always visible to the naked eye. The in- 
cluded, and the isolated glands as well, are often flattened, especially 
when the secretion which elevates their upper surface, has exuded, 
but they never become cup-shaped, and very rarely a few isolated 
hemispheres may be seen on the upper cuticular surface if carefully 
searched for. The axillary scale appears to be formed by a thicken- 
ing of the epidermis of the midrib and of the leaf, the fleshy growth 
finally embedding and partially burying the glands in its substance, 
while the thickening itself eventually becomes glandular. 
THE MATURE LEAVES OF PAULOWNIA IMPERIALIS, LIEB. 
Some of the books state that the mature leaves of Paulownia 
may be distinguished from those of Catalpa by their larger size. 
This distinction may be good in theory, but it fails in practice. The 
