354 IMPORTANCE OF REGISTERS 



ones : we can then be sure of observing the same in 

 two successive seasons, and we can choose those 

 which grow in spots that are well ventilated, where 

 they are neither too much sheltered, nor exposed to 

 the unnatural warmth of a south wall. With regard 

 to trees, such should be selected as grow in the open 

 fields, not in woods, where they are very unequally 

 screened from atmospheric influence. 



(16.) The directions for observers, issued by M. 

 Quetelet, give rules also for judging of the exact 

 epoch of leafing, flowering, &c., in any particular 

 case. Thus, in regard to leafing, we should choose 

 the moment when the first leaves are so far expand- 

 ed as to bring their upper surface into contact with 

 the atmosphere, from which time the commence- 

 ment of their vital functions is dated. The flowering 

 is determined by the petals or corolla being suffi- 

 ciently open to shew the anthers, which will apply 

 equally well to the flowers of the family of the Com- 

 positee, as to other cases. The fructification is regu- 

 lated by the dehiscence of the pericarp, at least in 

 dehiscent fruits, which are the great majority : in 

 indehiscent fruits, it must be determined by their 

 being manifestly ripe, and arrived at maturity. 

 Lastly, the time of defoliation should be considered 

 as come, when the greater part of the leaves of the 

 year are fallen : it being well understood that what 

 concerns the leaves applies only to the woody plants; 

 moreover excluding evergreens, in which the defolia- 

 tion takes place at successive periods.* 



* In the above remarks upon M. Quetelet's plan, we have not 

 made any allusion to his proposed horary observations on the 



