POE Kes EEE (eR E Ste ame as 
1878. ] Glandular Hairs of Plants. 281 
The function of glandular hairs in some cases is a great mystery. 
In the case of Martynia the writer found it caught immense num- 
bers of small insects, and in some way seems to suck out their sub- 
stance. Small insects are found to a greater or less extent caught 
and held fast by the glandular hairs on all or most of the plants 
which produce glands. In his Insectivorous Plants Mr. Darwin, 
by experimenting, concludes that the glands of Droseras devour 
animal substances. The same conclusion is reached in case of 
numerous other plants, as some Saxifragas, Primulas, Pelargo- 
niums, Pinguiculas, 
The glands of the trumpet creeper are active, even till the fruit 
is of full size and quite near maturity. They are much visited by 
flies, wasps, and especially by ants to such an extent that the 
plant is often considered a nuisance when placed near the house. 
The glands on the leaves of cherry trees and Viburnum are also 
much frequented by insects. ‘ The base of the leaves of the sun- 
flower, locust, Pteris aquilina (a fern) and numerous other plants 
are freely visited by insects. Of what benefit it can be to Tecoma, 
Pteris, Helianthus and the cherry to be thus visited by ants is be- 
yond my certain knowledge. 
The glands of tomatoes, tobacco, petunia and many other 
plants secrete a substance which is offensive to most insects and 
other animals which might otherwise devour the plants. 
r. Darwin has also shown that some of these plants do cer- 
tainly absorb and appropriate gaseous and liquid bodies. Many 
ingenious experiments were made on plants of several different 
orders, showing that “they detect with almost unerring certainty 
the presence of nitrogen.” Plants by their glands were fed with 
green-peas, raw meat, a decoction of grass leaves. These sub- 
stances “are acted on in exactly the same manner as by gastric 
juice.” 
Why may not these glands also draw nourishment from the 
particles of dust which fall on them from the air, or from the parti- 
cles of soil which in many cases accumulates to such an extent as 
to completely cover some portions of the plant? As root hairs 
are active in absorbing materials from the soil including some- 
thing from solid substances, why should not these active glands 
absorb materials from the dust and fragments of soil? The free 
presence of the air and light may also assist in this supposed ac- 
tion. This covering of the plant by the particles of soil held by | Me 
