H. BOTANY. 37! 



daylight, at a temperature of 15 to 22 Centigrade. The in- 

 jurious effects of carbonic acid on germination, observed by 

 Saussure, were here confirmed. As regards the effect upon 

 the development of chlorophyl in the young plants, the au- 

 thor concludes as follows : 



"The experiments described suffice, as I believe, to show 

 the remarkably injurious effect of carbonic-acid gas on the 

 verdure and growth of the plants. The presence of only two 

 per cent, of carbonic acid in the air becomes noticeable, es- 

 pecially by its effect on the formation of chlorophyl. ... In 

 an atmosphere which, with an amount of oxygen equal to 

 that in the air, contains one-half carbonic acid, not only was 

 there no growth, but the plants after a short time perished." 



This effect of carbonic acid upon the plantlet, while living 

 at the expense of the reserve nutriment in the seed, the au- 

 thor regards as very remarkable, in view of the fact that 

 green leaves in such a medium decompose the carbonic acid 

 with considerable energy. He remarks: 



"Since the green plants are, in virtue of their. capacity for 

 decomposing carbonic acid, in condition to build up their 

 substance from inorganic material, they create for themselves 

 at the same time the condition of growth at the expense of 

 material already assimilated." 



These observations have, in the opinion of the author, an 

 important bearing upon the theory that, before and during 

 the period of carboniferous deposits on the surface of the 

 earth, the atmosphere contained very much more carbonic 

 acid than at present. lie says : 



"In view of the fact that plants visibly sicken in an at- 

 mosphere which contains but a small percentage of carbonic 

 acid, we must conclude that, in an atmosphere not much rich- 

 er in carbonic acid than that now existing, a part, at least, of 

 the present vegetation of the earth would perish. But from 

 this, one of two things must follow. Either the composition 

 of the terrestrial atmosphere must always have remained the 

 same, as must necessarily be inferred from its boundlessness ; 

 or, as seems to me more probable, plants must have exist- 

 ed in former geologic periods capable of enduring larger 

 amounts of carbonic acid in the atmosphere." 



Boelim has also studied the effects of pure oxygen upon 

 the germination of seeds. Seeds moistened and placed in 



