PERIODICAL OPENING AND CLOSING OF FLOWERS. 3 



ment in particular plants, establishing, meanwhile, some allied 

 inquiries on the relative conditions of Vegetation, and their 

 dependence on season and other circumstances. 



The motion of the petals in all plants which have a regular 

 corolla may be compared with the motion of two connected lines 

 which form an angle with each other, which may be exactly 

 estimated in every position. 



The opening and closing of blossoms are very rarely momentary, 

 but are in general slow and continuous processes, which at all 

 hours of the day are in varying degrees of intensity, and by no 

 means bear any regular ratio to the time which has elapsed 

 since the commencement of the phase, but still subject to laws, 

 which can be numerically enunciated, when the nature of the 

 phenomena and their dependence on the contemporaneous inci- 

 dents in the immediate neighbourhood of the plants shall be 

 recognised. Thence arises the necessity of noting hourly through 

 the whole day and the entire duration of each particular blossom 

 the magnitude of the change which has taken place and the 

 relations of coincident meteoric phenomena. 



It was therefore obviously necessary to have constant access to 

 the plants under observation, though the results would necessarily 

 be somewhat modified, still to a degree more or less appreciable, 

 by the artificial conditions in which they were placed. The 

 series of observations, after certain preliminary steps during the 

 six preceding years, was commenced by Mr. Fritzsch, in earnest, 

 at the beginning of 1844, and was kept up with scarcely any 

 intermission for four years, his sister and wife giving him most 

 important assistance in his inquiries, without which, in fact, it would 

 have been almost impossible to have made any satisfactory progress. 



Indigenous plants were carefully removed from their native 

 place of growth and planted in pots, old individuals being used in 

 preference to seedlings as possessing greater vigour ; a point of 

 the greater consequence as the confined situation in which the 

 observations were made required as speedy a change as possible 

 of the species to be examined. Exotic plants were placed for 

 examination in the same place with those which w r ere indigenous, 

 the individuals being necessarily such as could conveniently be 

 procured, sometimes in the pots in which they had been raised 

 from seed or cuttings, and sometimes immediately transplanted 

 like the indigenous species. At different times the aspect in 

 which the plants were set varied from East and West to South, 

 and consequently in very different positions as regards the direct 



b 2 



