220 PHYSIOLOGICAL BOTANY. PART II. 



they emit little or no odour by day ; and several of 

 these as the night-scented stock, geranium, wallflower, 

 gladiolus, &c., are further remarkable from possess, 

 ing a peculiar brown and lurid tint. The flowers of 

 the splendid Cereus grandiflorus begin to expand about 

 seven o'clock in the evening, attain their full beauty 

 and put forth their powerfully fragrant odour before 

 midnight, and are completely faded before sunrise. 

 Some of the singular tribe of Stapelias are disgustingly 

 nauseous in the scent which they emit, strongly resem- 

 bling the most offensive carrion ; so much so indeed 

 that even flies and other carnivorous insects are de- 

 ceived by the similarity, and very frequently deposit 

 their eggs in their blossom. 



(211.) Impressions made by Odours. The scents 

 emitted by certain flowers make very different impres- 

 sions upon the nerves of different people; and some 

 persons can readily perceive a powerful odour where 

 others are nearly or entirely insensible to its impression, 

 although they may not be defective in other instances in 

 the sense of smelling. Very deleterious impressions are 

 made on some constitutions by the odours of strong- 

 scented flowers. The most dangerous symptoms have 

 occurred in persons especially females with weak nerves, 

 merely by their remaining in a room where certain 

 flowers have been placed ; and even violets are not 

 exempt from a bad reputation. Instances of death 

 have been recorded which were considered to have 

 been occasioned by effects of this kind ; and Linnaeus 

 mentions a case where the odour from the Rose-bay 

 (Nereum oleander} was supposed to have proved fatal 

 to the constitution of one person. Prussic acid may 

 be instanced as abounding in the leaves of the common 

 laurel (Pr units lauroceratus) to so great an extent, 

 that if one of them be cut into small pieces and placed 

 under a wine-glass, and a wasp or other insect be in- 

 troduced under the glass it will be completely stupefied 

 in two minutes. 



(212.) Excretions. We have still to allude to 



