72 
COROLLA. 
5th. Papilionaceous, a flower with a 
banner, two win^s, and a keel; thf? 
name is derived from the word papi- 
Ho, a butterfly, on account of a sii})- 
posed resemblance in form, as the 
pea-blossom, Fig. 78. 
If a corolla is not, in form, like any 
of those we have desci bed, it is said 
to be anomalous. 
of Flowers. 
The odour of flowers has its origin in the volatile oils, elaborated 
by the corolla ; its production results from causes both ^.eternal and 
internal, but, in bqth 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 httle odour. But 
if the heat is neither too great nor too little, the volatile oils exhale 
without being dissipated, forming a perfumed atmosphere around 
the 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 effect upon the nerves, and that it 
IS dangerous to respire, for any great length of time, even the most 
agreeable of them, in a concentrated state. 
One important office of the corolla, is to secure those delicate and 
important organs which it encloses, the stamens and pistils, from 
all external injury, and to favour their development. After the 
germ is fertihzed 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 furnish 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 
petal being furnished with an artery which conveys the vegetable 
blood to its extremities, exposing it to the hght and air under a 
delicate moist membrane ) this vegetable blood, according to his 
theory, is then collected and returned in correspondent veins, for 
Papilionaceous — What corollas are anomalous'?— Orij^in of the odour of flowers — 
Odour affected by temperature— Odour affected by moisture— Odours so etimes dis- 
agreeable—Dangerous if respired for along time— Office of the corolla— Darwin'* 
aeorv with reispeet to the coroUit 
