Page:The Journal of Indian Botany.djvu/186

 in the fact that the latter part is much more open. The initial level of the valley is of course higher in Lahoul than in Pangi.

There are absolutely no Liverworts beyond the Inner range. Of the other cryptogams only one alga which looked like a spirogyra was seen. No fungus, but two or three lichens were observed. One or two species of mosses were noted near running water. Only a single fern plant was seen but unfortunately was not identified. The flowering plants of this interesting region would be dealth with at a later date. It may perhaps be mentoined by the way that red snow due to the unicellular alga Chlaydomonas'jiivalis was observed just below the Baralacha pass on the south side at about 16,000 ft.

The facts of vertical distribution on the southern slopes of the Outer Himalayas can readily be explained by the increase in the rain-fall with the increase in height up to a certain limit after which the very low temperature acts as an adverse factor.

One interesting result as regards vertical distribution is that both the highest and the lowest genera of the Marchantiales are met with at the highest and the lowest levels. The lowest genus Eiccia is represented by B. robusta at Lahore (700 ft.) and at Lahoul (11,000 ft.). Of the highest genus Marcharitia, M. nepahnsis and M. palmata are very common in the plains and the outer Himalayas up to about 7,000 ft., while 1/. polymorplia goes up to about 11,000 ft. in the Chandrabhaga valley. Another genus, Grimoldia, about midway between the lowest and the highest genera is also widely distributed in this region. The only Indian species, G. indica, is very common from the foot of the Himalayas to about 11,000 ft.

The horizontal distribution is not so easy to explain. That the rainfall is not an essential factor is shown by the fact that it does not differ very much in the different places where collections have been made. Probably temperature connected with a higher latitude has something to do with it. The problem requires more study.

In the Ravi valley the rainfall is not a very important factor as it is not very high and isaccompanied by a comparatively low temperature, and Liverworts are thus generally met with only near permanently moist places. A few occur otherwise.

In the Beas valley (Kulu) although the rainfall is not very high but the broad valley is surrounded by hills on all sides and at higher levels there is a luxuriant Liverwort flora which compares very well as regards the number of species and individuals with localities further to the east.

In the Chandrabhaga valley rainfall does not count as a factor at all in the distribution of Liverworts. It is very small and therefore