PRINCIPLES OF VENTILATION. 249 



to the qualities and quantities of certain atmospheric elements 

 which plants are capable of sustaining in deficiency or in excess. 

 And the one or the other of these conditions appears to some of 

 the species a natural and even a necessary circumstance. The 

 degree in which vitality is sometimes retained by plants, under 

 the most unfavorable conditions, for a period to which it is diffi- 

 cult to assign a limit, is one of the most interesting and curious 

 circumstances in their economy. Instances have been related 

 of the growth of bulbs, unrolled from among the bandages of 

 Egyptian mummies. Although there is good reason to believe 

 that deception has been practised on this point, upon the credu- 

 lity of travellers, still there is nothing impossible in the asserted 

 fact. Light, heat, and moisture are the cause of the development 

 of these curious structures, and their forms become expanded 

 under the additional agency of atmospheric air. Now, when 

 removed from the influence of these, there is no reason why a 

 bulb, if it can remain unchanged for ten years, should not do so 

 for a hundred ; and if for a hundred, why not for one thousand 

 years ? The vitality of seeds under similar circumstances 

 appears quite unlimited. ^ 



In the first chapter of this treatise, we have ventured to assert 

 that light is of more importance to plants than air, although we 

 are aware that this point is open to much discussion, from the 

 fact of some plants being adapted to thrive under the almost 

 total deprivation of it. These, however, will generally, if not 

 solely, be found to consist of plants in the lowest orders of 

 organization, such, for instance, as the algae, some of which, pos- 

 sessing a bright green color, have been drawn up from the depth 

 of more than one hundred fathoms, to which the sun's rays can- 

 not penetrate in any appreciable proportion ; and also the fungi, 

 which have been found growing in caverns and mines to which 

 no rays from the sun, either direct or reflected, would seem to 

 have access. These facts, however, do not greatly aflect the 



* Melon seeds have been known to grow at the age of 40 years, kid- 

 ney beans at 100, sensitive plant at 60, rye at 40, and there are now 

 growing, in the garden of the Horticultural Society, raspberry plants 

 raised from seeds 1600 or 1700 years old. — [Lindlei/s Introduction to 

 Botany. \ 



