On the Structure and Functions of the Organs of Respiration. 281 



liberation of carbon appears to be the effect of the conversion of the original 

 proximate principles of the seed, into those more fitted for the support of 

 the young plant j as, for instance, that of starch or hordeine into sugar. 



The changes which take place during flowering, are very similar to those 

 produced by germination. A large quantity of oxygen is converted into 

 carbonic acid by the action of the flower ; a considerable quantity of heat 

 is developed j and it is believed that the fecula previously contained in the 

 disk, is changed by this process into saccharine matter, adapted for the 

 nutrition of the pollen and young ovula; the superfluous portion flowing 

 off in the form of honey. It is remarkable that this analogy between ger- 

 mination and flowering holds good, not only in their products, but in the 

 conditions requisite for their development. Neither will commence, ex- 

 cept in a moderately warm temperature ; both require moisture, for flowers 

 will not open, unless well supplied with ascending sap ; and the presence 

 of oxygen is in each case necessary. It is an interesting fact, that, after 

 many trials, it has been found that germination takes place most readily in 

 an atmosphere, consisting of one part oxygen, and three parts nitrogen, 

 which is nearly the proportion of the air we breathe. If the quantity of 

 oxygen is increased, the carbon of the ovule is abstracted too rapidly, an4 

 the young plant is feeble ; if the proportion is smaller, carbon is not lost 

 in sufficient quantity, and the young plant is scarcely capable of being 

 roused into life. 



In studying the changes produced during the flowering of plants, we find 

 a direct relation between the carbonisation of the air and disengagement of 

 caloric, and the development of the glandular disk. This is especially re- 

 markable in the Arum, where a thermometer, placed in the midst of a mass 

 of inflorescence, has been seen to rise to 121° j while the temperature of 

 the external air was only 06°. From the experiments of Saussure, it ap- 

 j)ears that the disengagement of heat, and the disappearance of oxygen, are 

 principally caused by the action of the organs of fecundation. The Arum 

 Italicum, whilst in bud, consumed in twenty-four hours, five or six times 

 its volume of oxygen ; during the expansion of the flower, the spadix being 

 hot, thirty times j and when the flower was withering, five times. When 

 the floral envelopes were removed, the quantity of oxygen consumed by the 

 remaining parts, in proportion to their volume, was much greater. In one 

 instance, the sexual apparatus of the Arum Italicum consumed in twenty- 

 four hours, one hundred and tiiirty-two times its bulk of oxygen, Saussure 

 also observed that double flowers, in which petals replace sexual organs, 

 vitiate the air much less than single flowers, in which the sexual organs 

 arc perfect. 



The truth of these statements, which have been questioned by manv 

 eminent observers, has recently been placed beyond all doubt, by the ex- 

 periments of Adolphc Brongniart upon Colocasia odora. (Nouv. Ann. du 

 Mas^-um, vol. iii.) He ascertained that during the emission of the pollen. 



