to some extent protect other birds, and has therefore, at any rate, that advantage.
It is very remarkable, considering how long we have lived on this globe with other animals and plants, how little we know about them; and yet there is intense interest in unravelling the secrets of nature.
I do not allude to difficult problems which require physical laboratories and observatories, nor to those which can only be solved by technical study. The formation of the blood, for instance, is still a mystery; and it is certainly an extraordinary thing, considering the great importance of blood in the animal system, that we do not yet know how or where it is produced. There are many other questions of the same kind which might be mentioned, but which, though of great importance, hardly came within the range of such a Society as our own.
Even, however, as regards the habits and life of our commonest animals and plants, there are still an immense number of interesting problems remaining to be explained and solved.
Perhaps the commonest of all English plants is Pleurococcus vulgaris, the little alga or seaweed which covers the stems of trees, palings, and other woodwork of a similar character with a coating of green. It consists of small rounded cells, sometimes quite separate, sometimes grouped together in little packets of two, four, or eight. These divide and subdivide, and multiply in this manner. But obviously this is only a part of the life-history of the plant. Like the rest of its family it probably, at certain times and under certain conditions, produces spores; but all this part of its life-history is quite unknown. In the case of the common mushroom, again, the spores are of course enormously abundant, and yet nothing is known about their germination.
Peas, beans and other leguminous plants almost invariably have swellings or tubercles on their roots. These are supposed to be produced by bacteria, and when such tubercles are present great quantities of nitrogen are accumulated. An important result of this is that leguminous crops are supposed actually to enrich the soil. In Germany, in many places, the yellow lupine is especially grown for no other purpose but to be ploughed in and thus improve the soil for other crops. These bacteria are
