72 COROLLA. 



5th. Papilionaceous, a flower with a 

 banner, two win^s, and a keel; the 

 name is derived from the word papi- 

 lio, a butterfly, on account of a sup- 

 posed resemblance in form, as the 

 pea-blossom, Fig. 78. 



If a corolla is not, in form, like any 

 of those we have described, it is said 

 to be anomalous. 



Odour of Flowers. 



The odour of flowers has its origin in the volatUe ofls, elaborated 

 by the corolla ; its production results from causes both external and 

 internal, but, in both cases, equally beyond our observation. Tem- 

 perature renders the odour of flowers more or less sensible ; if the 

 heat is powerful, it dissipates the volatile oils more rapidly than they 

 are renewed: if the heat is very feeble, the volatile oils remain con- 

 centrated in the little cells where they were elaborated ; under these 

 circumstances the flowers appear to possess but little odour. But 

 if the heat is neither too great nor too little, the volatile oils exhale 

 without being dissipated, forming a perfumed atmosphere around 

 tlie flowers. 



You perceive the reason, that when you walk in a flower garden 

 in the morning or evening, the flowers seem more fragrant than in 

 the middle of "the day. The air being more charged with humidity, 

 is another cause of an increase of fragrance at those times ; as the 

 moisture, by penetrating the delicate tissue of the corollas, expels 

 the volatile oils. There are some exceptions to the laws just stated ; 

 for some flowers are only odorous during the night, and others 

 during the day. Some flowers exhale fetid odours, which attract 

 such insects as are usually nourished by putrid animal substances. 

 Many flowers exhale sweet odours ; but, however odours may differ, 

 in the sensations which they produce, it is certain, that powerful 

 ones have a stupifying, narcotic eflect upon the nerves, and that it 

 is dangerous to respire, for any great length of time, even the most 

 agreea'ble of them, in a concentrated state. 



One important oflace of the corolla, is to secure those delicate and 

 important organs which it encloses, the stamens and pistils, from 

 an external injury, and to favour their development. After the 

 germ is fertilized by the influence of the pollen, the corolla fades 

 away, and either falls off" or remains withered upon the stalk ; the 

 juices which nourished it then go to the germ, to assist in its growth, 

 and enable it to become a perfect fruit. 



Another use of the corolla seems to be, to fiirnish a resting-place 

 for insects in search of honey. 



The corolla is supposed by Darwin to answer the same purpose 

 to the stamen and pistils, as the lungs in the animal system ; each 



Eetal being furnished with an artery which conveys the vegetable 

 lood to its extremities, exposing it to the light and air under a 

 dehcate moist membrane ; this vegetable blood, according to his 

 theory, is then collected and returned in correspondent veins, for 



Papilionaceous— What corollas are anomalous 1— Origin of the odour of flowers — 

 Odour affected by temperature— Odour affected by moisture— Odours sonietimea dis- 

 agreeable-Dangerous if respired for a long time— Ofl&ce of the corolla— Darwin'i 

 Eeory with lespect to the corolla. 



