DownIE—CHINESE SPECIES oF TSUGA. 15 
and grooved on the upper surface are either white underneath 
or concolorous. ‘The one year twigs vary from a distinct yellow 
to a red-brown colour, the apex of the pulvinus invariably being 
redder or darker than the rest of the twig. 
The anatomy of the leaf did not help very much in the system- 
atic placing of the species. What differences I have found 
merely substantiate the formation of the two main groups. A 
difference in outline is maintained in a general way throughout 
the groups. Inthe Yunnanensis group there is a deep groove on 
the upper surface and a slight midrib on the lower surface, while 
the angles of the leaf are sharp. In the Chinensis group the groove 
on the upper surface is very slight and there is no midrib on the 
lower surface while the angles of the leaf are rounded. Excep- 
tions, however, occur. "The deep groove on the upper surface is 
absent in some leaf sections of Ward 1666, belonging to the 
Yunnanensis group (all sections were taken near the middle of 
the leaf) and sharp angles were observed in serrated species of the 
Chinensis group, so that variability in outline must be expected. 
The distribution of the hypodermal cells on the other hand has 
proved quite a constant factor. In both groups the arrangement 
on the lower surface is the same, a few cells beneath the resin 
canal and a few in scattered groups or continuous between the 
angle of the leaf and the beginning of the stomatic area. The 
difference is found on the upper surface. In the Yunnanensis 
group hypodermal cells are practically absent, a few cells sub- 
tend the deep groove only. In the Chinensis group all species 
show a large development of hypodermal cells in groups all along 
the upper surface or forming a continuous layer beneath the epi- 
dermis. 
Key to the Species. 
A. Leaf apex entire; cones strictly sessile; leaf margin serrul- 
ate; branchlets pubescent; hypodermis on upper surface 
restricted to groove. 
I. Cone scale woody in texture, smooth. 1. Tsuga dura. 
II. Cone scale fibrous in texture, finely longitudinally striate. 
: : ; ; : ‘ : Ze unnanensis. 
B, Leaf apex emarginate; cones shortly stalked; leaf margin 
serrulate or entire; branchlets pubescent; hypodermis 
scattered all along upper surface. 
TI. Cone scales patent at maturity. : 4.4, paens. 
II. Cone scales erecto-patent at maturity. 
a. Leaves generally serrulate on margin. 
i. Scales up to 14 x 13 mm. about 25 per cone. 
‘ . 4. T. Wardu. 
4 . 
