Books and Current Literature. 



67 



soil was collected. In any event, Professor Hall informed me 

 that he first noticed the specimen six years ago. At that time 

 it was already a large and thrifty fern. Thinking that there 

 might possibly be some leakage of gases through the old seal, 

 he resealed the bottle with paraffin, applying the new seal 

 without any disturbance to the old. We may be sure, therefore, 

 that during the last six years absolutely no interchange of 

 materials between the interior of the bottle and the outside 

 has taken place. It is indeed probable that the old seal never 

 leaked, and that this condition has obtained throughout the 

 life of the plant. 



Moisture, salts, organic matter, and various micro-organisms 

 were undoubtedly present in the soil at the time it was sealed 

 up. A certain amount of free oxygen was, of course, included 

 above the soil. Light entered through the glass, the temperature 

 conditions were favorable and the plant grew normally. The 

 carbon dioxide of the air was replenished from the decay of 

 organic matter in the soil, the original amount of moisture was 

 always present, and by photosynthesis new carbohydrates were 

 formed, the fern thus increasing in size and in number of leaves. 

 The old leaves died and fell upon the moist soil, there to be 

 gradually decomposed through the action of organisms, and 

 thus carbon dioxide was set free which diffused into the air 

 to be again fixed by the photosynthetic process in the living 

 leaves above. This cycle of carbon interchange must have 

 gone on many times, the energy source therefor being, of course, 

 the light that penetrated through the walls of the bottle. Theo- 

 retically, at least, there seems to be no limit to the length of 

 life of such an hermetically sealed plant, so long as the light and 

 temperature conditions remain adequate. 



BOOKS AND CURRENT LITERATURE. 



Studies in Mesa and Foothill Vegetation, University of Colo- 

 rado Studies, Vol. VI, No. 1, is the first of a series, of which 

 the present number includes Geology and Physiography of the 

 Mesas near Boulder, by Gideon S. Dodds; Climatology of the 

 Mesas near Boulder, by Francis Ramaley; Distribution of Coni- 

 fers on the Mesas, by W. W. Robbins and Gideon S. Dodds; 



