6  HutTCcHINSON—THE MADDENI SERIES OF RHODODENDRON. 
the terminal leaf-bearing buds Professor Balfour makes some 
interesting remarks at the end of the description of R. Valen- 
tintanum on p. 49. 
Leaves.—These are always evergreen, and more or less cori- 
aceous in texture; they persist for at least three years; in 
shape they vary from linear (R. iteaphyllum) to obovate (R. 
Dalhousiae and R. Scottianum), and ovate (R. voseatum), rounded, 
obtuse to acutely cuneate at the base; frequently, especially in 
subseries Ciliicalyx, they are fringed with long hairs (R. ciliatum, 
R. formosum, and others) ; the upper surface on the unfolding 
of the leaves is almost without exception lepidote, the scales 
soon falling off; a characteristic feature of R. burmanicum is 
that they persist on the upper surface and are nearly as dense 
there as on the lower surface; the lower leaf surface is always 
lepidote, and the disposition of the scales provides a useful 
and apparently very constant specific mark ; for instance, in R. 
Maddeni they completely hide the lower epidermis, whilst in 
R. Lindleyt and R. ciliicalyx they are considerably more than 
their own diameter apart; the distance apart relative to their 
own diameter seems to be the most lucid way of expressing the 
disposition of the scales; were it measured in terms of milli- 
meters or fractions thereof, the distinctive marks as shown by 
the scales would not be so readily interpreted; the structure 
of the scales is on the same general plan throughout the series ; 
the stalk of the scale is more or less fleshy, and a little immersed 
below the level of the surrounding leaf surface; the stalk 
supports the membranous fringe, which encircles it and spreads 
horizontally over and in close proximity to the leaf surface; 
the fringe of the scale is made up of numerous radiating parallel 
cells arranged in a single row; I have not considered it worth 
while to count the number of these fringe cells, but they might 
prove to be relatively constant in the same species, and would 
perhaps differ sufficiently in the various species as to provide 
additional distinctive characters; between the scales the 
epidermal cells are always produced into a rod-like or bluntly 
awl-shaped papilla; these are a very marked feature * in the 
leaves of the whole series, and readily detected by a low power 
of the microscope; they are not visible through an ordinary 
hand lens; the midrib in subseries Eumaddenia and Ciliicalyx 
is always more or less sunken below the upper surface of the 
leaf blade, whilst in subseries Megacalyx it is raised; this 
impression and elevation of the midrib is accompanied by a 
marked difference in the Petiole ; those leaves with an impressed 
midrib have always petioles with a concave upper surface and 
* In R. ciliicalyx they tend to disappear in cultivation under certain con- 
ditions ; see p. 53. 
