THE FARMER'S MAGAZINE. 



289 



and the whole is enclosed in a coat of dense vege- 

 table matter. 



The growth of the seed consists in the develop- 

 ment of the germ into a perfect plant, and is 

 known as germination. Supposing the conditions 

 of growth to be favourable, the first preliminary 

 is a softening of the coat of the seed, by which 

 means water gains an entrance, and having per- 

 vaded the mass, causes it to swell freely. When 

 the water reaches the germ of the seed, the gluten 

 or albuminous matter near to it undergoes a 

 chemical change, and we have a very important 

 and powerful body formed which is known as 

 diastase. Whether or not the germ in any way 

 participates in this change, we have no pooof; but, 

 if not, it is certain that at least by its presence it 

 exerts a controlling power. The same addition 

 of moisture to any other portion of the seed would 

 not produce the same effect, for this agent (dia- 

 stase) is only found in close proximity to the germ, 

 and its existence in the seed appears to be simul- 

 taneous with the first stage of germination. Upon 

 the diastase thus formed devolves the important 

 office of preparing food for the growth of the 

 germ ; for the bulk of the seed, although abund- 

 ant in quantity and exactly suitable in its constitu- 

 ent elements, is not ready for use until it has 

 become soluble in water, and thus been made 

 capable of entering into the circulation of the 

 germ. This is accomplished by means of the 

 diastase, by the agency of which the necessary 

 supplies are prepared, so long as the store of food 

 in the seed is needed. An immediate extension 

 of the cellular matter accompanies the entrance 

 of the food into the circulation, and we have the 

 external evidence of life by the sprouting of the 

 seed. In whatever position the seed may be placed, 

 the radicles at once strike perpendicularly down 

 into the soil, and the tender rootlets fix themselves 

 there with but little delay. As soon as this is ef- 

 fected, the gemmule grows in the opposite direction 

 and becomes developed into the stem and leaves 

 of the plant. 



The conditions which control the growth of 

 seedb are, the presence of air, moisture, and 

 warmth ; and to produce healthy germination, all 

 are required in definite proportions. When seed 

 is protected from these agencies it will retain its 

 power of growth for long periods of time. Thus, 

 wheat, preserved in Egyptian mummies between 

 3000 and 4000 years, has, after that lapse of time, 

 germinated and produced a large increase. The 

 preservation of the power of growth is entirely 

 dependent upon the seed being kept from those 

 agencies which would excite its vital energy : 

 moisture is the first essential for germination, as it 

 is in consequence of the chemical action excited in 

 the seed by thg entrance of water that the seed is 

 aroused to action ; and after this process of 

 growth has been excited, if it become checked, it 

 cannot be renewed. This shows the necessity of 

 keeping seeds dry when they are not required to 

 germinate. Moisture alone is not sufficient for 

 this process of growth, as the seed requires a 

 supply of atmospheric air to enable the necessary 

 chemical changes to proceed. Stagnant water in 

 the soil must of necessity be unfavourable to ger- 



mination, because it renders the land cold and 

 excludes the free access of air, both of which con- 

 ditions are prejudicial. 



The exceptioDS to this rule are very few : one, 

 however, may be found amongst agricultural seeds 

 in the floating sweet water-grass (G/^j/cem/wi/ajts), 

 grown in our water-meadows, in which instance 

 immersion in water is absolutely necessary for the 

 growth of seed. In this case we have a seed which 

 has the power of extracting its supply of air from 

 water — a power which but very few other seeds 

 possess. The supply of air is as necessary for 

 these aquatic seeds as for any others ; for if we 

 drive out the air from water by boihng, they can no 

 longer germinate. For the same reason, seeds 

 which are buried deeply in the earth, remain there 

 for many years, not because they want moisture, 

 but because it is unaccompanied by the presence 

 of atmospheric air. The earth raised from wells, 

 or brought from railway cuttings, or ploughed up 

 by a furrow of extra depth, often becomes covered 

 by a growth of vegetation, the produce of seeds 

 which have long been dormant in the soil. 



Warmth is another essential condition for ger- 

 mination, which, within moderate hmits, is rendered 

 more rapid by an increase of temperature; but 

 it must be accompanied by a proportionate increase 

 of moisture, otherwise it becomes destructive. 

 The action of heat promotes chemical changes in 

 the seed, but a free supply of water is necessarry, 

 not only that it may exert a like chemical influence, 

 but also because it enters largely into the more 

 delicate body into which the dry matter of the 

 seed has to be transformed. Thus we see that 

 healthy germination depends upon the com- 

 bined action of the three agents— heat, water, and 

 air. 



The opinions which are entertained respecting 

 the influence of light are conflicting. Some con- 

 sider that hght retards the process of germina- 

 tion, whilst others consider that it does not influence 

 it prejudicially. The experiments which have been 

 made, although far from conclusive, are calculated 

 to favour the former opinion; for the growth, 

 although equally perfect, has not been as rapid 

 under the action of light as when the seed has 

 been covered from it. We know that, as soon as 

 the seed has made sufficient growth to throw out 

 its leaves, the action of light is favourable, its pre- 

 sence enabling the plant to decompose carbonic 

 acid and to retain the carbon for its own, whilst 

 the oxygen is thrown off into the air. But at this 

 earlier stage of existence, or, in other words, 

 during the period of germination, growth is fa- 

 voured by an action just the reverse of this. The 

 seed and its sprouts want to absorb, not to throw 

 off oxygen, and to emit instead of taking in 

 carbonic acid. During germination, then, the 

 action of light would tend to paralyse the vital 

 powers of the seed, and limit its growth to the 

 hours of darkness, instead of allowing the develop- 

 ment to be continuous. Another great advantage 

 gained by covermg the seed is the more equable 

 supply of moisture which is preserved beneath the 

 surface, as well as the better opportunity afforded 

 to the roots for firmly fixing themselves in the 

 soil. 



