TRANSACTIONS OF SECTION K. 683 
8. Plant Breeding at St. Andrews. By Dr. J. H. Wiuson. 
9. The Botany of the Abor Expedition: A Study of the Forests of the. 
Abor Hills, Eastern Himalaya. By I. H. Burxinn, M.A. 
The author had the fortune in 1911 to be named by the Government of India 
botanist to the Abor Expedition. Leaving Calcutta in November, he joined the 
force at. Kobo, in the plain of Upper Assam, and proceeded into the hills of the 
Abors, where nearly four months were spent in exploring the dense forests near 
the Dehong River up to 6,200 feet. 
Forest is the natural clothing of the Abor hills, where it obliterates the clear- 
ings of man quickly; and where woody plants, following herbs, invade the less 
inviting spots (1) as epiphytes securing places in the tree-tops, (2) slowly spread- 
ing on to the rivers’ sterile sandbanks, and (3) invading the river-beds between 
their June level and their January level. The author used his time chiefly in 
studying the constitution of the different types of forest met with, and these 
three intrusions. 
The Plains forest is in a way a northward extension of the vast forests of 
Malaya. Like all tropical rain-forests, it has a great variety of foliage. It has 
three layers—(1) the layer of the wind-dispersed, relatively small-leaved, giant 
trees; (2) the layer of the animal-dispersed, large-leaved, lesser trees not grow- 
ing beyond the still air; and (3) the layer of the ground vegetation wherein the 
plants are not large-leaved except in the alleyways of the forest. The second 
and third layers are separated by a light-diffusion space. 
In their relation to creepers the trees of the forest differ in interesting ways : 
some thrive by outgrowing the creepers in annual spurts ; some thrive by smother- 
ing them. : 
The Lower Hill forest is of two kinds. On the south slopes it is not unlike the 
Plains forest; but on the north slopes rules a most distinct and characteristic 
forest composed chiefly of a tree called by the Abors ‘Shingkeng.’ There is 
little variety in the foliage of a Shingkeng forest. Above the base of the hills 
oaks appear, and rule in places. On very steep slopes a giant bamboo rules. 
‘The Upper Hill forest has very uniform foliage, and is rather of two layers than 
three. 
Grasses, as in the Sikkim forests, are very rare in the whole countryside; it 
is only where the very copious rain is drained away to an unusual extent that 
they can exist: thus, the very steep slopes harbour the giant bamboos; Abor 
clearings on hill-crests enable Saccharum to exist for a while; very well trodden 
paths in the immediate vicinity of villages allow two species to grow; sandbanks 
grow grasses; one invades the river-bed, clinging to rocks; and the gravel-beds at 
the foot of the hills after cultivation become covered with Phragmites. 
Elsewhere grasses, even on clearings returning to jungle, do not exist. The 
clearings after the crop is removed are seized on by Ageratum, Bidens, Blumea 
Gnaphalium, Triumfetta, Viola, &. Then follow shrubs out of which a Calo- 
phyllum and a Macaranga gradually come to rule, the foliage getting larger as 
the height of the scrub increases, until finally it passes back to the true forest. 
he river’s clearings are sandbanks. Grass, first of all, takes possession of 
them; then slowly trees invade them, those which come first being the most 
deciduous species of the countryside. 
The fall of the River Dehong in the hills is 50 to 60 feet. Of terrestrial plants, 
a moss ventures furthest into the exposed river-bed; not quite so far ventures a 
Jungermannia; a fern, an Hquisetum, a Polygonum, and the curious Euphor- 
biaceous HHomonoia descend to a limit which has a longer period above the flood ; 
another Hquisetum, two other ferns, and Rhabdia of the Boraginacee descend 
half-way ; the grass already mentioned, a Lactuca, a Blumea (Composite), Viola 
Patrinii, a Ficus, and some other plants occupy in increasing degree the upper 
part of the banks. The grass makes such a dense mat of roots as to resist the 
wash of the current and to hold a soil. The Homonoia is a tree with a trunk 
buried in the shingle. : 
Humid all the year round, it is only on the bluffs and south slopes of the Abor 
hills that trees bare after their leaf-fall for more than a month are found. 
Where bare trees stand, the epiphytes of the upper layers of the forest can be 
