26 DR. 7. E. Т. AITCHISON ON THE BOTANY OF 
much shorter than that in the tropical zone, the weather is intensely hot while it lasts, 
no dew falling under an altitude of 3500 feet. These extremes of temperature between 
summer and winter and night and day are much intensified by the absence to the north 
of any mountain-range affording adequate shelter from the continuous blasts of bitterly 
cold wind in winter and of hot dry air in summer, coming from the north-east and north- 
west respectively. The mountains in the vicinity not being suffieiently high to retain 
perpetual snow, the water-supply is limited to the rivers Hari-rud and Morghab and to 
a very few perennial springs. 
With such climatic conditions cultivation, below an altitude of 3500 feet, is impossible 
without the aid of irrigation, except under the ameliorating influences of a river; and 
until the dew-line is gained it is a land totally devoid of trees or even shrubs. But as. 
soon as this point is reached Pistacia vera, Juniperus excelsa, and Lonicera nummulari- 
folia appear as forest-trees, and wheat and barley no longer need irrigation. 
I may mention here that my collections do not wholly consist of what is usually 
regarded as the oriental flora, for they contain a considerable admixture of Siberian and 
Central Asiatic types ;. and doubtless the proportion of the latter would have been larger 
had I been able to collect at greater altitudes, as it is there where the greatest over- 
lapping of the two elements occurs. There are also а few Western Himalayan or Tibetan 
plants, and a very limited number common to the Punjab and Scind regions. Тһе local 
species comprise, in all probability, one sixth of the whole collection. 
I met with no indigenous Conifere except Juniperus excelsa, but Pinus halepensis 
is cultivated. There were no oaks, nor any species of the genera ZZseulus, Olea, or 
Myrtus. 
The tropical zone, spoken of by Hooker and Thomson as skirting the Afghan region, 
does not extend to the north-west, owing to the excessive fall in the winter temperature 
and the shortened summer; a conclusive proof of this is the absence of the date-palm. 
The area of Pistacia Terebinthus, var. mutica (Kinjak), is limited to the southern aspect of 
the Do-shakh range. А few subtropical shrubs from Scind and the Punjab do just 
exist through the low winter temperature, namely, Peganwm Harmala, Prosopis Ste- 
phaniana, Alhagi Camelorum, and Capparis spinosa, with the grasses Hrianthus Ravenne 
and Andropogon laniger. Populus euphratica forms forests in the river-beds ; but as 
long as this treeis situated near water, it is indifferent to altitude, being known to extend 
from Scind and the Punjab to Western Tibet, up to a height of 12,000 feet. А more 
curious extension is Haloxylon Ammodendron from the apparently dry shifting desert 
sands of Baluchistan to the river-beds of this area. Pulicaria foliosa is the only plant 
collected whose area extends from India proper (Banda, in Bandelkhand, on the Jumna 
river) to this region. 
. Among the Himalayan types met with were Sisymbrium himalaicum, Sophora mollis, 
Rosa moschata (cult.) Prangos pabularia, Pterotheca Falconeri, and Epilasia ammo- 
phila, with several of the Chenopodiaceous shrubs found in the arid Tibetan region. Of 
species common to Central Asia I may name Nigella integrifolia, Corydalis Sewerzovii, 
| Isatis Boissieriana, Crucianella filifolia, Kuschakewiczia turkestanica, Convolvulus sub- 
hirsutus, Astragalus buchtormensis, and Orobus subvillosus. 
