64 PERIODIC PHENOMENA OF VEGETABLE LIFE. 



recently those of Quetelet,* Dove,f Fritsch, J and several others. 

 These last observations, in particular, not only comprise a long 

 series of years, hut apply to a considerable number of plants, and 

 thus afford comparable results. I found it very instructive to 

 compare the observations quoted and the results obtained with 

 analogous deductions made in the Alps. 



2. Delays in the development of Vegetation, occasioned by altitude. 

 — I have endeavoured in the following table to give a mean com- 

 mencement of different periods of vegetation, according to 

 differences of altitude of 1000 feet each. It is based upon data 

 contained in detailed tables of periods of vegetation in different 

 localities. I have had occasion also to make numerous isolated 

 observations which have assisted in obtaining these means, whilst, 

 at the same time, I composed these data with other isolated 

 observations previously published. It has been my object thus to 

 obtain results as general as possible, to enable me to follow out 

 the influence of altitude and of the consequent climateric changes. 

 The nature of these phenomena, and the local influences to which 

 they are subject, § cause the period of their commencement to vacil- 

 late over a considerable space around the meau deduced. These data 

 are therefore more extensive than those which might be deduced 

 from other observations, such, for instance, as temperature. || 



* Instructions sur I' Observation des Phenomenes Periodiques, 1840, in 

 Vol. I., Part I., of the Bulletin de I' Academic royale de Bruxelles. On the 

 Climate of Belgium, Phenomenes Periodiques des Plantes, 1846, from the 

 Annates de rObservatoire royal de Bruxelles. The above contains very- 

 detailed comparisons of the first parallel observations known, a review of 

 the means of from six to four years, and new series of remarks. The 

 collected observations of several stations are being published annually by 

 Quetelet, iuthe Nouveaux Memoires de V Academic des Sciences et Belles-lettres 

 de Bruxelles. 



*t* On the connexion of variations in Atmospheric Temperature with the 

 development of Plants, 4to. 1846, from the Memoirs of the Academy of Berlin 

 for 1844, and from the Monthly reports of the Academy, for 1846. 



On the relation of Atmospheric Temperature to the development of Plants, 

 after the observations of M. Vogt, at Arys, in East Prussia, from the 

 monthly reports of the royal Academy of Berlin, for 1850. 



X In the Annals of the Observatory of Prague, by Kreil, commenced in 

 1840, and On the Periodic Phenomena of Vegetable Life in the Annals of 

 the Royal Academy of Sciences of Bohemia, Prague, 1847. 



§ We shall advert farther on to the great deviations from the general 

 means in special seasons and at special stations. 



II Some irregularities in different plants will still be found in the accom- 

 panying table ; it has not been always possible to separate them from the 

 actual observations made, nor to investigate more attentively their causes. 

 As it is the endeavour iu these researches to compare the analogous 

 periods of vegetation in several plants, it would be much to be wished that 

 the mean results obtained could be much freer from similar perturbations. 



