ON VEGETABLE PHYSIOLOGY. 71 



no repose ; and if requisite, a large proportion of 

 their species are without its benefits, since a great 

 many of them never close their leaves excepting 

 when they approach to decay. A more probable 

 cause of this phenomenon will be found in the 

 provision which nature has made to guard the 

 more tender plants and the flowers (always deli- 

 cate) against the operation of cold ; so that when 

 the usual excitements of light and heat are with- 

 drawn, they close their leaves as a necessary 

 precaution.* 



Having finished our account of the nutritive 

 agents of plants, we are next led to consider the 

 organs employed by nature for their re-produc- 

 tion ; and these, as we have before stated, consist 

 of the flower, fruit and seed. 



It is well understood, that upon the early ad- 

 vance of vegetation, there are to be seen some- 

 times upon the stem, frequently upon many of 

 the bulbous roots, and always upon the branches, 

 very small prominences denominated the gem 

 or bud, containing the rudiments of future for- 

 mations; some expanding into leaves and new 

 branches, some into flowers, and some into flow- 

 ers and leaves conjointly. 



The flower gem, to which our attention now 

 must be exclusively directed, by the progress of 

 vegetation, gradually expands and enlarges until 



* Upon this subject, however, very different explanations 

 have been given by naturalists. 



