OF THE SEED AND GERMINATION. 



109 



imbibe moisture, and swell out and burst its in- 

 teguments. The moisture thus absorbed is im- 

 mediately imbibed by the cotyledons or albur- 

 num, and i chemical action soon takes place. 

 The farina and oily matters entering into its 

 composition, form an emulsive juice, and a fer- 

 mentation takes place, by which a saccharine 

 matter is generated, and carbonic acid gas is 

 evolved. This process is well exemplified in 

 the case of the conversion of barley into malt. 

 In the barley, the starchy matter of the seed is 

 changed from an almost tasteless and inodorous 

 substance, into sugar; oxygen gas is absorbed, 

 carbonic acid given out, and the greater pro- 

 portion of the seed converted into a nutritious 

 substance for the future genn. 



Now, the question is, how does the absorbed 

 oxygen operate? Does it act simply as a stimu- 

 lant, or does it enter into combination with the 

 materials of the seed, to form a new substance ; 

 or does it abstract from the seed any principle 

 by which the subsequent changes are effected. 



Humboldt was of opinion, that the oxygen 

 Bcts merely as a stimulant, and this opinion was 

 founded on the fact, that seeds germinate faster 

 in pure oxygen, than in the common atmospheric 

 air; and particularly if the seeds were previously 

 steeped in water containing oxymuriatic acid. 

 This philosopher found that seeds brought from 

 the East and West Indies, which would not ger- 

 minate at Vienna, in the usual manner, did so 

 readily when steeped in oxymuriatic acid, even 

 though they had been kept for upwards of 

 twenty years. 



RoUo was of opinion, that the absorbed oxy- 

 gen is partly taken up by the seed, and assimu- 

 lated with its substance, forming, along with the 

 carbon of the seed, carbonic acid. His opinion 

 was founded on the following fact, which he had 

 observed in watching the process of the germin- 

 ation of some grains of barley, confined in an 

 artificial atmosphere. When the seeds were 

 made to germinate in pure oxygen gas, the oxy- 

 gen gradually disappeared, and its place was 

 found to be occupied by carbonic acid gas. 



Saussure the younger, having also directed 

 his attention to the subject, perceived tliat the 

 only means of ascertaining the fact was, that of 

 comparing the quantity of oxygen gas consumed, 

 with the quantity entering into the composition 

 of carbonic acid gas evolved. If the quantity 

 of the former proved to be greater than that of 

 the latter, it was to be inferred that a portion of 

 oxygen gas had been actually assimilated to the 

 substance of the seed. But if the two quantities 

 proved to be constantly equal, then it was to be 

 inferred that the oxygen gas had not been assim- 

 ilated to the substance of the seed, but only 

 employed for the purpose of abstracting from it 

 part of its carbon, in the formation of carbonic 

 acid gas. From the experiments of Lavoisier 



on combustion, he had discovered that oxygen, 

 in combining with carbon, undergoes no percep- 

 tible alteration of volume, and that one hundred 

 cubic inches of carbonic acid gas, contains 

 ninety-eight cubic inches of oxygen gas. From 

 these facts, Saussure instituted a series of ex- 

 periments to ascertain the proportion between 

 the quantity of oxygen inhaled; and the quan- 

 tity of carbonic acid evolved. For this purpose 

 he employed the seeds of peas, beans, barley, 

 lettuce, and cress, and the results were as follows. 

 In an atmosphere of 100 cubic inches of com- 

 mon air, known to contain about twenty-one 

 cubic inches of oxygen, and seventy-nine of ni- 

 trogen, where a number of these seeds were made 

 to germinate, it was found that if fourteen cubic 

 inches of carbonic acid gas were fonned during 

 the process, seven cubic inches of oxygen gas 

 remained unoombined in the atmospher.;; and if 

 seven cubic inches of carbonic acid gas were 

 formed during the process, then fourteen cubic 

 inches of oxygen gas remained uncombined in 

 the receiver. Hence it appeared that the quan- 

 tity of carbonic acid gas that was evolved dur- 

 ing the process of germination, was jjrecisely 

 equal to the quantity that had been absorbed 

 during the same process. There was conse- 

 quently no actual accumulation of oxygen in 

 the seed, the portion of this gas absorbed having 

 gone to diminish the quantity of carbon. The 

 change, therefore, produced in the farina of the 

 seeds of plants, by which it is converted into a 

 saccharine juice fit for the nutrition of the genn, 

 or infant plant, consists in diminuting the pro- 

 portion of its carbon, and in augmenting that 

 of its oxygen and hydrogen. Humboldt, as we 

 have already mentioned, found that seeds could 

 be made to germinate in pure oxygen gas, and 

 in a shorter period of time than in ordinary air. 

 But Saussure, in repeating these experiments of 

 Humboldt, did not find any difference in the 

 periods of gemiination. The only difference 

 was in the comparative lengths of the roots, 

 those seeds which had been made to germinate in 

 pure oxygen, having their radicles less developed 

 in a given time, than the others in common air. 

 This circumstance, according to Mr Keith, may 

 be accounted for in two ways. The oxygen, in 

 its pure state, might have abstracted too great 

 a quantity of carbon from the seed; or the car- 

 bonic gas, evolved in too great abundance, might 

 have been prejudicial to the development of 

 the young plant. For it has been found that 

 carbonic acid gas is not useful to vegetables in 

 genez'al, except in proportion as they can decom- 

 pose it; and seeds before the development of the 

 plumulet, do not seem capable of effecting that 

 decomposition; so that, the application of car- 

 bonic acid, in almost any proportion, rather re- 

 tards than accelerates the first process of ger- 

 mination. Saussure also found that different 



