CHAP. III. FUNCTION OF NUTRITION. 219 



these cases they are readily convertible by some natural 

 process into a nutritious emulsion; and then appear to 

 be destined to feed the young plant during the early 

 stages of its development. 



The following table shows the percentage of fixed 

 oil obtained from the seeds of a few plants : 



Nut - - 60 



Cress - - 58 



Walnut - 50 



Poppy - - 47 



Almond - - 46 



(210.) Taste and Scent of Plants. It will readily 

 be conceived that the peculiar tastes and odours met with 

 in different species, must depend entirely upon the nature 

 of the various matters which are secreted by them. 

 Attempts have been made to classify the various im- 

 pressions which are thus made upon the sensorium, and 

 odours have been arranged into classes, under the 

 terms aromatic, foatid, acrid, alliaceous, musky, &c. 

 Such classifications at the best are highly empyrical, 

 and any arrangement which could be founded on an 

 accurate knowledge of the chemical nature of these 

 substances would be far preferable ; but our extreme 

 ignorance on these points will not justify the attempt 

 at present. The delicate perfumes emitted by certain 

 flowers, as well as the more powerful and often disagree- 

 able scents afforded by the herbage of some plants, 

 generally depend upon the diffusion of a volatile oil. 

 In some cases this oil is magazined in the stalks and 

 leaves, and is rendered more sensible the more these 

 parts are rubbed or bruised. In the flower especially, 

 the oily particles which produce the odour seem to be 

 diffused as fast as they are secreted ; and hence it hap- 

 pens that the greater number of plants are more power- 

 fully scented at one particular part of the day and 

 that almost all flowers are most fragrant towards night. 

 There are some, specially termed " night-scented," 

 which are extremely powerful after sunset though 



