_Over-ripening of Grain._--The final act of vegetation is the production of seed, after the performance of which function many plants, having accomplished their destined purpose, perish. The grasses (which include the cereals) are _annuals_, or plants which have but a year's existence, consequently their development ceases so soon as they have produced their seed. When wheat, oats, and the other cereals, attain to this final point in their growth, the circulation of their sap ceases, their color changes from green to yellow, and they undergo certain changes which destroy their power of assimilating mineral matter, and consequently render them no longer capable of increasing their weight. The proper time for cutting wheat and the other cereals is immediately after their grain has been fully matured. When the green color of the straw just below the ears changes to yellow, the grain, be it ripe or unripe at the time, cannot afterwards be more fully developed. This is rendered impossible in consequence of the disorganisation of the upper part of the stem--indicated by, but not the result of, its altered hue--which cuts off the supply of sap to the ears, and the latter do not possess the power of absorbing nutriment from the air. When the vital processes which are incessantly going on in the growing plants are brought to a close, the purely chemical forces come into operation. If the seed be perfectly matured and allowed to remain ungathered, it is attacked in wet weather by the oxygen of the air, a portion of its carbon is burned off, some of its starch is converted into sugar, and in extreme cases it germinates and becomes _malty_. But not only is the seed liable to injury from the elements; it is also exposed to the ravages of the feathered tribe, and no matter how well a field of corn may be watched, or how great the number of _scarecrows_ erected in it, there is always a certain diurnal loss, occasioned by the ravages of birds.