1S39] 



FARMERS' REGISTER 



333 



principles result, which, by being soluble in water, 

 are easily made use of by the plant. The pro- 

 duction ot sugar in this case, identifies the change 

 which the seed has undergone, with what is termed 

 the saccharine lermentation. The circumstances 

 which are favorable to the production of the sac- 

 charine lermentation in vegetable matter, are well 

 known ; they are, a temperature from 60° to 70° 

 Fahr., the presence of moisture, and the free ac- 

 cess of atmospheric air. J^et us see how fir obser- 

 vation will justify us, in applying the remark to 

 the germination of seed. 



Isf, With respect to the temperature best adapted 

 to the germmation of seed. No seed has ever 

 been known to germinate at or below the freezing 

 point ; hence seed do not germinate in vvinler, even 

 though lodged in their proper soil. The tempera- 

 ture most fiivorable to germinal ion, varies widely in 

 different species; seeds being known to (germinate 

 at almost every temperatu.-e between the freezing 

 and boding points of water. Nearly all plants in- 

 digenous to temperate climates, require a tempera- 

 ture of at least 50'^ Fahr. for germination ; the 

 precise temperature in each varying with the pe- 

 culiar constitution of the species ; a circumstance 

 which explams the regular succession noticeable 

 in the leafing of difl'erent trees, and in the appear- 

 ance of annual herbaceous plants, during the 

 spring and summer. We are not, however, to 

 infer from this that the particular temperature 

 at which the seed of any plant usually germinates, 

 is the most favorable which is possible for its ger- 

 mination. Adanson found that seed which will 

 germinate at ordinary temperatures in the space 

 of twelve liours, may be made to germinate in 

 three hours, by exposing them to a "reater dei^ree 

 of heat. 



2nd, The presence of moisture. Seed will not 

 germinate if they are kept perfectly dry. Water, 

 or some similar lifiuid, is essential to germination ; 

 hence seed sown during a drought will never grow 

 until the rain has moistened the ground in which 

 they are deposited. But the (]uantity of water 

 present is not a matter of indifference ; for it is 

 found that if there be two much water present 

 the seed wili rot. The quantity of water required 

 by dilli'rent seeds is not the same. Some can bear 

 but little water, whilst others will germinate when 

 partially immersed, as has been proved by an ex- 

 periment of Du Ilamel, at least in the case of peas. 

 When he placed peas so that they should be about 

 half immersed in water, he found that they ger- 

 minated as freely as if placed in the soil ; but much 

 more than this they could not bear, for when to- 

 tally immersed they rotted. There are some seed 

 however, which will germinate when totally im- 

 mersed, as must necessarily be the case in the 

 seeds of aquatic plants. 



3rd, The access of atmospheric air. Seed will 

 not germinate if placed in vacuo. Ray introduced 

 some seed of lettuce into the receiver of an air- 

 pump, and having exhausted the air, he let them 

 remain for some time, but no germination ensued ; 

 he then readmitted the air, and the seed ger- 

 minated after the usual period had elapsed. It'has 

 also been ascertained by experiment, that seed 

 Will not germinate either in nitrogen, carbonic 

 acitl, or in hydrogen gas ; and hence we conclude 

 that it is the oxygen of the atmosphere which is 

 essential to germination. 



The influence of light, which is so favorable to 



growth in all the subsequent stages of vegetation, 

 is injurious to the germination of the seed. Sen- 

 nebier has provecl that a seed germinates more 

 rapidly in the shade, than in light, and in diffused 

 dr.ylight, than when exposed to the direct rays 

 of the sun. The reason of this is, that light ef- 

 fects the fixation of carbon in the tissues, a liard- 

 ening process, exactly the reverse of that which 

 takes place in germination. Soil is by no means 

 essential to the germination of seed; the retjuisite 

 nourishment tor the young plant during the first 

 stages of its (rrowth being deposited in tfie seed 

 itself at the time of its formation. The embryo 

 requires only the joint influence of air, moisture, 

 and a proper temperature, to enable it to grow, 

 and appropriate this nourishment to its own use. 

 Yet soil, in consequence of its mechanical texture, 

 permitting, as it does, the free access of air, and 

 excluding the light, is very favorable to ger- 

 mination. Besides these circumstances, it is gen- 

 erally necessary that the seed should have reached 

 full maturity in order to germinate well. Tills 

 however is not always the ccse. The seed of the 

 sacred bean of India (^cyamus nelumbo) will some- 

 times germinate whilst it is yet in the capsule and 

 connected with the parent plant. The same is 

 true of the seed of the mangrove, a tree which 

 grows along the borders of tlie sea in tropical coun- 

 tries. Whilst the seed of this plant is yet in the 

 pericarp, its young radicle pierces the seed vessel, 

 and elongates until it reaches the soft mud in 

 which such trees grow, where it takes root, and 

 afterwards separates from the parent plant. These 

 instances however must be considered as ex- 

 ceptions to a general rule. 



The period necesary to complete the process of 

 germination, is not ttie same in all plants, even 

 where all the conditions necessary to germination 

 are fulfilled. Some species require a shorter, and 

 others a longer period. The grasses are among 

 the number of those plants whose seeds germi- 

 nate most rapidly, and rosaceous plants among 

 those which germinate most slowly. The follow- 

 ing table indicates the period of germination of a 

 considerable variety of seed, as determined by 

 Adanson. 



When seeds are protected from the action of 

 those agents whicfi facilitate germination, they 

 may generally be preserved for a long time ; but 

 even in ilie most fiivorable circumstances, they at 

 length lose the power of germinating. The period 

 during which seeds preserve their vitality, varies 

 much in difl'erent species, and also in the same 

 species, in ditlerent circumstances. An exposure 

 of a \'e\\ weeks is sufficient to destroy the vitality 

 of many seeds; especially those which are covered 

 with a thin and delicate skin. On the other hand, 

 all hard bony seeds, such as those of the pea tribe, 

 may be kept fijr many years, without material 

 detriment to their germinating power. Seeds of 

 the sensitive plant (cassia nictitans') have been 

 made to grow after an interval of 26 years; and 

 peas, taken from a collection of seed made by 



