526 Rivet t .■ — The Anatomy of Rhododendron ponti cum, L. } and of 
35 cm. in length. Though often described as xerophytic in character, it 
has been observed that they are more liable to suffer from drought than the 
laurel and the Aucuba , with which they are sometimes associated in 
decorative shrubberies. The year’s growth of a shoot is very characteristic. 
The winter-bud is enclosed by scales which are morphologically entire 
foliage leaves reduced in s*ze : in the spring the internodes between the 
scales elongate considerably and the scales themselves enlarge slightly, 
so that they assume a form transitional between scales and true foliage 
leaves. They are rather delicate in texture and fall off after a short time, 
leaving a narrow scar, which half encircles the stem. . In the early part of 
the summer the true, persistent foliage leaves are developed. They are 
often very large, 12 to 15 cm. in length, and xerophytic in character. The 
petioles are thick and terete, leaving a circular scar where the leaves fall. 
They are not separated by well-marked internodes, but are crowded 
together in a rosette-like form. The length of the internodes is short but 
extremely irregular. The position of the leaves in the full-grown shoots is 
not affected by. the light, so that the shoots retain their radial form, but 
there is a certain two-sidedness apparent, due to the greater growth of the 
leaves on the abaxial side of the axillary shoots, and on that side of the 
leading shoots away from the centre of the bush. The shoots are not fully 
matured at the end of the first season’s growth, being softer and more 
flexible than they become later. In the axils of the lowest deciduous 
transitional' leaves, buds are rarely developed, though they may appear in 
the upper ones. In the axils of the foliage leaves are large protected buds, 
which may remain dormant some time before they develop. The larger 
buds are on the abaxial side of the shoots. When the shoot terminates in 
a flower-bud, all the large axillary buds, some of which may remain dormant 
in a vegetative shoot, develop into an apparent whorl of lateral branches. 
These grow about 25 cm. in length in their first season and may terminate 
either vegetatively or in a flower- bud. In the former case the shoot con- 
tinues its growth monopodially for the next season with a possible whorl of 
smaller laterals immediately below it. 
Material . For this investigation the material consisted of mature 
shoots of one season’s growth. These were in groups as they had been 
borne on the previous year’s shoot, which was cut from the shrub near its 
apex. The groups are lettered and figured in Diagram I. The A group 
consisted of A 1, a main stem borne monopodically, and A 2, A 3, A 4, all 
lateral shoots. In the B group, B 1 is monopodial, B 2 and B 3 axillary. 
In the C and D groups, C 1 and D 1 are monopodial and the others axillary. 
In the E group there is no leading monopodial shoot, as the terminal bud 
had either been replaced by a flower or had aborted, but there are five 
axillary shoots, E 2 to E 6, of which E 2 assumes the form of a leading 
shoot. The groups were cut early in February J919. The persistent leaves 
