of the Climate of Naples upon the Periods of Vegetation. 279 



In those five years the maximum heat was found to reach 

 30° Reaum. (100° nearly Fahr.) on the 7th of August 1824, 

 and the minimum was — 2 0, 8 Reaum. (about 26° Fahr.) on 

 December 30th, 1822.] 



Now to prove the truth of the principle before stated with 

 regard to heat, it will be sufficient to observe that the seeds 

 of the plants of hot climates, introduced into temperate cli- 

 mates, germinate very much later than they do in their native 

 countries; whilst the germination of the seeds of cold cli- 

 mates is remarkably accelerated by their being transported 

 into temperate climates. For the sake of an application to 

 this same principle, we are obliged in the stoves of our botanic 

 gardens to raise the heat to a very high point, in order to 

 make the seeds of the equinoctial countries sprout; and on 

 the contrary, for the growth of those of the northern climes, 

 we must select the colder and more shady situations. 



The different temperature which usually predominates in 

 the same seasons in different years likewise exercises its great 

 influence in retarding or accelerating the germination of seeds ; 

 inasmuch as we see that the seeds of tlie same plant sprout 

 very much sooner when the spring begins early, and is pre- 

 ceded by a mild and rainy winter; and that they are later 

 when the spring is kept backward by the severity of a long 

 winter which has preceded it. Thus I have had occasion to 

 observe in the Royal Garden at Naples, that the plants which 

 I have caused to be sown in March or April have grown im- 

 perfectly at the very same period, that is to say, when the 

 temperature rises between 12° and 15° Reaum. (or 59° and 

 66° nearly Fahr.); consequently, I have become quite indif- 

 ferent whether they be sown a month sooner or a month 

 later. This observation, repeated for many years in succes- 

 sion, the experiment being always made at the risk that 

 the plants which had lately sprung up encountered, when 

 they were exposed to the hoar frost, and to the cold nights 

 in the beginning of spring, has induced me to decide very de- 

 finitively, that in the Royal Botanic Garden the large seeds 

 ought not to be sown before the last 1 5 days in April or the 

 first 15 days in May*. 



[To be continued.] 



• * It is worthy of remark what very little difference exists between the 

 time here fixed, and the usual vernal seed-time in England. 



