OF PERIODIC PHENOMENA. 343 



MOLLUSKS. 



Time of land and freshwater species quitting their respective 



winter retreats. 



of coupling, and laying their eggs. 

 of hatching of the young. 



The above heads of periodic phenomena relate to 

 the animal kingdom. In the vegetable kingdom the 

 observer should notice 



With respect to Phanerogamous Plants. 



Time of the sap's rising in trees, indicated by the swelling of the 

 buds.* 



Time when the first leaves open. 

 when in full leaf. 



Times of leaf- 

 ing, &c., 

 comprising 



when second, or midsummer, shoots appear.t 

 when leaves begin to change, 

 when change becomes general, 

 when leaves begin to fall, 

 when trees stript of leaves. 



* An observer has suggested, that, with respect to buds, it 

 would be very interesting to note, at least in the case of some of 

 the principal trees, whether at the end of the season they were 

 much or little developed. With this view, we might give the size 

 of them towards the end of October, by measuring their longitu- 

 dinal and transverse diameters. He attaches much importance to 

 such observations, from the circumstance that the rapidity with 

 which the leafing takes place the following spring, and even the 

 time of leafing, do not depend so much on the temperature of the 

 spring, as on the degree of development to which the buds had 

 arrived previously to winter. Phenomenes periodiques du Regne 

 Vegetal. (Extrait du torn. ix. No. ii. des Bulletins de 1'Acad. Roy. 

 de Bruxelles.) 



t The same observer alluded to in the last note thinks that the 



