102 BOMBAY NATURAL HISTORY SOCIETY. 
season gets in, is quite glabrous below, only glandular-pubescent on 
the upper parts, and quite scentless. The common Blumea Wigh- 
tiana is distinguished by its dense, almost velvety pubescence, and a 
most pleasant mint-like fragrance ; it grows with its nesrally, Blumea 
(now Laggera) aurita on rnbbish-heaps, and as a weed of the cold 
season in gardens and fields, The last-mentioned species is perhaps 
less hairy, but has a much stronger turpentine-like fragrance, as also 
the yellow flowered Blumea laccra, common on roadsides. Finally, 
we have the mountain forms, Blumea glamerata and Blumea 
Maleolmi, both of which are densely woolly, silvery white and 
strongly scented. 
ut also within the same species the degree of pubescence is 
very variable according to season of growth and locality. One of 
our most common weeds, Gynandropsis pentaphylla, is generally nearly 
smooth in the rains, brt at this time of the year always more or less 
hairy, and Hydrocotyle rotundifolia is glabrous in shady positions, 
but hairy when exposed to the sun. 
Similar observations with regard to other plants have led toa 
eorrect conception of the importance of hairs for plants. The 
protection they afford is manifold, chiefly against excessive heat; 
and I shall only mention a few of the more important capacities of 
the hairs. When closely set they shade the tender parts of plants 
against the burning rays of the sun, when very dense and white 
they reflect the heat; by force of capillarity they always absorb 
even the smallest quantity of moisture from the air, and finally they 
serve the plants by retaining the dew. 
In citing the various species of Blwmea, I laid stress on their 
fragrance. I did so, as this peculiarity is also highly protective 
against heat. You may all have experienced the cooling and refresh- 
ing effects of applying perfume to the skin, a circumstance, which 
I need hardly tell you is caused by the rapid evaporation of all 
essential oils. Now the fragrance of plants is due to exactly the 
same cause, evaporation of essential oils, and we may therefore 
conclude that such plants are constantly cooled and refreshed, in 
order better to resist the heat. But besides, Chemistry teaches us 
that the result of this mechanical action is the formation of resinous 
substances, which are probably deposited on the surface of plants 
_ and thus further check the evaporation, chiefly during the hottest 
and driest parts of the day. The viscidity of many aromatic plants 
tends to prove this view, 
