14 ^Outlines of Horticultural Chemistry. 



from immature seed are always weak in their growth, and 

 unproductive. Some seeds require to be sown immediately 

 after they ripen. The coffee bean, and the seeds of angelica and 

 fraxinella, refuse to germinate if not sown within five or six 

 weeks after they have been gathered ; but by far the majority 

 of seeds retain their powers of vegetating, if carefully preserved, 

 for years. Home sowed barley, which vegetated after being 

 gathered 140 years. Farinaceous seeds, that is, such as con- 

 tain a large proportion of starch, usually are those which retain 

 their vitality the longest (barley, wheat, and oats, are of this 

 number), inasmuch as that that constituent is very slow in 

 decomposing. Oily seeds, and those enclosed in juicy berries, 

 or other seed-vessels of a mucilaginous or saccharine quality, 

 are the most liable to spoil. It is to be observed that, for 

 the gardener, old seed is sometimes desirable ; the plants from 

 it run less luxuriantly in foliage, and produce their blossom 

 and fruit more early than those from new seeds : hence, for 

 melons, early and late crops of peas, &c., seed that is a year 

 or two old is to be preferred. 



No seed will germinate without oxygen gas, moisture, and 

 a certain degree of heat are present. The requisite propor- 

 tions of these vary in different individuals ; but, in the total 

 absence of any one, no seed will advance a single grade in 

 vegetation. When all are present to a seed, carbonic acid gas 

 is evolved, and oxygen absorbed. This gas is afforded to 

 the seed from the atmosphere, in which we shall see hereafter 

 it exists in the proportion of about 21 per cent. From the 

 experiments of Saussure we learn that, weight for weight, wheat 

 and barley, during germination, absorb less oxygen than peas ; 

 whilst these consume less than beans and kidneybeans. The 

 first two may, therefore, be buried at a greater depth below 

 the surface of the earth than the last three, without vegetation 

 being prevented ; for it is the want of a due supply of oxygen, 

 at great depths from the surface, that prevents the germination 

 of seeds so buried. Seeds that are thus situated, however, 

 will often retain their vegetative power for an apparently un- 

 limited period : hence earth, taken from a considerable depth, 

 will often, when brought to the surface, be covered with 

 thistles, charlock, &c. In botanic gardens, plants, that were 

 supposed to be lost to the establishments, have often been 

 recovered by the casual digging over tlie borders where they 

 had been grown ; some of their seed having been buried in 

 by a previous turning over of the soil. Seeds abounding in 

 oil have been observed to retain their vitality the longest when 

 so buried. 



