BY THE PRESIDENT. 
11 
which it comes in contact, whereas the probability is remote of 
this occurring in the case of those that approach flying. It is 
therefore an advantage to plants if creeping insects are prevented 
from reaching the flower. Plants growing in water require no 
special adjustment for this purpose, and many, such as the common 
teasel, obtain on dry land the same result through their stalks being 
at one place or another surrounded by water which has collected in 
a concavity formed by their leaves. An interesting adaptation is 
seen in Polygonum amphibium, which usually floats in water, and 
roots at the lower nodes. Under such conditions the leaves and 
stalks are hairless, but should the pond or ditch dry up, the stalk 
soon becomes covered with glandular hairs excreting a viscid matter 
which is an effective barrier to crawling insects. A number of 
plants, and among them the viscid lychnis ( Lychnis viscaria ), the 
ragged Robin ( Lychnis Jlos-cuculi ), and the Salpiglossis, are pro¬ 
tected in the same way. Indeed viscid stems, leaves, and calices 
are of frequent occurrence, and so effectual is the service that 
Kerner collected more than sixty species of insects from the flower- 
stems of Silene nutans. The same botanist mentions a curious ex¬ 
periment upon plants with a milky juice, such as lactuca angustana 
and L. sativa. Having placed ants upon them, he says he found 
that the ants were glued down by the juice which had exuded 
through the punctures made by the hooks of their feet in the 
uppermost leaves. We also find plants abandoning as it were any 
defence from unbidden guests, and obtaining the safety of their 
flowers by placing a portion or the whole of their nectar on their 
leaves or stipules, just as a friend of mine places her plate-basket 
on the stairs to prevent her from being disturbed by robbers. In 
Impatiens tricornis the two stipules of each leaf are transformed 
into nectaries. 
The ray-florets of the Compositse, as seen in the daisy, fold in¬ 
wards at night and during cold weather, so as to protect the disks. 
The closing of many flowers, such as the (Enothera , in the daytime, 
prevents visits from useless insects. 
The object of the different positions of many leaves at night 
from what they hold during day, is to protect their more sensitive 
upper surfaces from cold. In Trifolium repens , for instance, the 
two lower leaflets rotate, so that their upper surfaces are in contact 
and their position becomes vertical. The terminal leaflet falls over 
the edges of these two leaflets with its lower surface uppermost, 
while its two sides slope from the mid-rib like a roof. Of the 
plants that sleep at night the Rev. G. Henslow has shown that many 
of the young leaves at an early stage assume the position of the 
