Page:Popular Science Monthly Volume 50.djvu/587

Rh I can now trace in any of the ‘themes’ of which Prof. Channing thought so well. There is no greater mark of the progress of the university than the expansion of the electives to include the natural sciences. My own omnivorousness in study was so great that I did not suffer much from our restricted curriculum; but there were young men in my time who would have graduated in these later days with highest honors in some department of physics or biology, but who were then at the very foot of the class, and lost for life the advantage of early training in the studies they loved. Akin to this modern gain and equally unquestionable is the advantage now enjoyed in the way of original research. Every year young men of my acquaintance come to me for consultation about some thesis they are preparing in history or literature, and they little know the envy with which they inspire their adviser; that they should be spared from the old routine to investigate anything for themselves seems such a happiness."

Forests and River Flow.—Mr. C. C. Vermeule observes, in a report of the State Geological Survey on Forestry in New Jersey, that in estimating the relation of forests to the flow of rivers we should not consider the points of extremely high and extremely low water, but should look for the beneficial effects in the stages which prevail during the months of an ordinary dry period. "The soil and subsoil of a watershed," he says, "hold a large amount of water, which is fed out as drainage, in the form of springs and seepage, to the stream during dry periods. It is a matter of common observation that at such times rivers continue to flow when the rainfall is much less than the evaporation, and indeed for long periods when there is no rainfall at all. Anything which tends to increase the amount of water which is held in the ground, and to regulate its discharge into the streams, tends to give a larger flow, and to shorten the periods of very low water in the streams during droughts, and with this increased capacity of the ground to absorb rain come also less frequent floods. Humus in the forest forms a great sponge, and of itself holds a large amount of water, while it and the inequalities caused by tree roots, etc., tend to prevent the water flowing over the surface, and the roots of the trees provide channels by which the water percolates into the subsoil readily. In this way the forest will easily absorb a larger amount of water than open lands. A high state of cultivation also has a tendency to increase the capacity of the ground to absorb water, because of constant loosening of the surface and the facilities provided for ready drainage. In this way cultivation, like forests, tends to render floods less frequent, but the effect of the drainage of the soil is that the ground water absorbed is fed out more rapidly to the streams during the early months of a dry period than is the case in forests; consequently the ground water is sooner exhausted and the duration of the low stages of the rivers during protracted droughts is thereby lengthened. Barren watersheds offer less capacity for absorption of rainfall. There is no humus or other matter on the surface to retain the rain, and the ground becomes hard and resists free percolation."

Long-Lived Seeds.—M. Casimir de Candolle said, in an account in the British Association of experiments dealing with latent life in seeds, that seeds retain their germinating faculty for very long periods of time if kept dry and protected from all external influences which would produce changes in their physiological condition. The question as to what is their physiological condition during the period of rest is an interesting one. It is possible to conceive them as absorbing oxygen or as giving off carbonic dioxide. If the latter process takes place, the carbon must be supplied from the tissues of the seed itself. In that case would the seedlings produced from these seeds be normal? The author had raised perfect seedlings from seeds known to have been kept more than a hundred years. A remarkable instance of the length of time seeds may be preserved was afforded where, on clearing away heaps of rubbish which had been undisturbed for a long time in a silver mine in Greece, the ground over which the heap had lain became in a short time covered with a mass of plants, of which the seeds from which they sprang could not have been there less than fifteen hundred years. An Irish agriculturist in the audience said that certain fields