Meyen's Report for 1839 on Physiological Botany. 33 



hence it comes, that flowers in which the sexual organs are 

 much closed do not smell ; on the contrary, other flowers 

 smell strongest exactly in the dampest hours of the day and 

 night. 



In the second part of the treatise M. Trinchinetti considers 

 the odours in detail ; he says, that flowers which become odo- 

 rous towards the end of their existence, as for instance Asperula 

 odorata, produce this smell by the commencement of decom- 

 position, and that it is not a product of vitality ; that there are 

 flowers which, when pressed, evolve a different smell to what 

 they do in their natural state, e. g. Allium moschatum, Sambucus 

 ebulus, &c. Flowers which only smell in the morning, evening, 

 and night, lose their smell during the day by the action of the 

 light and heat, which dissipate the odorous principle ; but to 

 this M. Morren answers, that these plants do not even smell by 

 day when inclosed in a damp, dark place. Finally, the author 

 attempts to answer the question as to the cause of intermitting 

 odours : flowers which exhibit this phaenomenon either open 

 and shut at fixed periods, or they remain always open, and 

 only the smell is intermittent : thus the inquiry is divided into 

 two parts ; in the first the phaenomenon is brought in con- 

 nexion with the cause of the opening and shutting of the 

 flower, and in the second a peculiar physiological cause as 

 producing it is assumed. In the first case flowers are either 

 shut by day and open and odorous by night, or vice versa. In 

 the second part those plants are mentioned which are always 

 open, but possess an intermittent smell ; here are also two di- 

 visions, the flowers smell either by day or by night. In Oes- 

 trum diurnum the smell is much weaker by night. Coronilla 

 glauca smells only by day, and Cacalia septentrionalis is said 

 to lose its smell when protected from the rays of the sun. Pe- 

 largonium triste begins to smell about five in the afternoon ; 

 in the night the smell becomes stronger till about five in the 

 morning, whereupon it diminishes, and disappears entirely at 

 seven. The surfaces of these odorous petals are said to ex- 

 hibit in the evening shining corpuscles (cells filled with sap) 

 which are not seen in the day. If the plants were kept the 

 whole day in the dusk, the smell made its appearance later 

 than usual and was also much weaker. Moist air produced no 

 smell in the plants during the day ; on the contrary, Oestrum 

 nocturnum, kept in the dark and in a moist atmosphere, exhi- 

 bited a slight smell. 



On the Formation of Colours in Plants. 



M. Eisner has drawn attention to the fact, that in the year 

 1832, in a treatise in Schweigger-Seidel's Annual of Chemistry 

 Ann. $ Mag. N. Hist. Vol. viii. D 



