President's Address lxxxvii 
be fittingly mentioned here, namely, the means of protection which the 
seeds possess against injurious influences before they reach their final 
resting-place. I have already mentioned that the seeds of edible fruits 
are provided with a hard and bony coat. Others, that might be eaten 
on account of their size, are likewise protected by hard shells, or by 
poisonous or unpalatable substances ; others, again, are so small that 
they are not detected when once scattered about. As it is of great 
importance to plants that their seeds should be sown under favourable 
circumstances, we find many arrangements to prevent the scattering 
during wet weather. 
The involucres of the composites and the capsules of many plants 
close or remain closed when the increasing dampness of the atmosphere 
indicates approaching rain. Some of the finest illustrations of such 
barometer—or more correctly hygrometer—plants are afforded by many 
of our species of Mesembryanthemum, which not only mark the time by the 
punctual opening and closing of their bright flowers, but also the change 
of the weather by their capsules. When the air is damp, the flat capsules 
are closed with a more or less hemispherical top ; in warm sunshine, how- 
ever, the outer tissue of the wall dries, and contracts to such an extent 
that the teeth become quite recurved, forming a pretty star, and allow- 
ing the seeds to escape from the open cells when shaken by the wind. 
Another very interesting contrivance occurs on some Acanthacez. 
I stated above that the ripe capsules of most genera of this order 
contract in dry weather, and, bursting in consequence, they eject the 
seeds with considerable force. There are some, however, ¢g., Barleria 
(see Figs. 5 and 6), which do not open as long as they are dry, but 
burst with a sudden crack when moistened, the seeds remaining in the 
valves. The seeds lock then quite different from what they were when 
dry. Seeds from capsules which had not been moistened as yet are 
lentil-shaped, and show a wrinkled surface, caused by closely adhering 
hairs. In the moistened state, however, each seed floats in a drop of 
mucilage derived from the instantaneously swelling hairs. If such a 
seed dries again, the hairs do not collapse into their former position, 
but some remain standing and form a radiated wing around the seed, 
evidently adapted to transport by the wind. Hence we see that the 
mucilaginous hairs serve two purposes: they assist in the spreading of 
the seeds, and absorb the moisture necessary for their germination. 
With these remarks I must close the description of the different 
means which our plants possess for securing the distribution of their 
seeds and the propagation of their kind. The list is by no means 
complete, many plants being as yet unknown to me in their fructiferous 
state, and the present paper is simply a first attempt to deal with a 
subject of vast extent. 
