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FORMATION OF SEED.

duction of organic matter, the substances so formedare retained and stored up in itself, and the fruit orseed-vessel not only returns nothing to the plant onwhich it grows, hut in addition attracts to itself a largeportion of the vegetable matter formed, or, to speakscientifically, assimilated, by the leaves.

350. Thus, whilst the leaves are continually addingnew matter to a plant, the fruit, on the other hand,by absorbing that matter, checks the growth. Hence,also, the practice of pruning fruit-trees with a view toimprove the fruit; the young fruit thus gets an ad-ditional supply of crude sap, which would otherwisehave gone to the formation of fresh leaves had not thebranches been removed.

351. It must not, however, be supposed that theformation of flowers and seeds is similar to the forma-tion of woody fibre, or leaves ; very different changestake place, but the same general conditions are requiredby plants in both cases.

352. Flowers do not, like leaves, possess the power ofdecomposing carbonic acid under the influence of light ;on the contrary, flo-wers appear at all times to give outcarbonic acid. From this it is evident that they mustconsist principally of substances containing in proportionless carbon than the ordinary proximate principles, suchas gum and lignin. There is a common belief that plantsin blossom deteriorate the air, and, therefore, that theirpresence in bed-rooms is highly objectionable. It is truethat flowers generate carbonic acid; but it is probable