170 THE AUSLRALIAN NATURALISI. 
ARIL OF CUPANIA AND SYNOUM. 
By Miss A. A. Brewster. 
An Avril, arillus a wrapper, is an extension of the placenta en- 
veloping the seed, as the mace surrounding the nutmeg. Arils 
vary in size and shape and often get special names according to 
their form. The fleshy aril on a castor seed is often called a 
caruncle. The fleshy ring around the funiculus (stalk) of many 
seeds of Leguminosae example Hardenbergia, may be termed a 
strophiole. The term aril or arillus is usually more strictly ap- 
plied to the layer-like covering of seeds such as Cupania. The 
aril of Strelitzia is in the form of a brilliant red cup-like cover- 
ing of fibrous texture. : 
At Nielsen Park there are a number of Cupania trees. The 
structure of the seed and the development of the latter can be 
watched from the earliest stages, as many young and old fruits 
fall to the ground. In very young seeds the aril forms a 
little cup in which the tiny seed is located. As the seed matures 
the aril grows upwards, completely enveloping and growing be- 
yond the seed. The upper edge of the aril is somewhat fringed 
and serrated. Folds occur in the upper part of the aril, the 
seed being thus safely tucked away as in a bag. During these 
stages the aril gradually changes from green to orange-yellow; 
later the seed grows more rapidly, turns black, and finally, when 
the seeds are shed, the aril is brilliant red, forming a tightly- 
fitting cup above which part of the black seed protrudes. 
The use of the aril when the seed is mature is undoubtedly to 
“attract the attention of birds, and so aid in dissemination. But 
the excessive growth of the aril just before the complete ma- 
turity of the seeds suggests that there is some other use for it, 
and this may be that it acts as a blanket to raise the temperature 
of the seed, and so aid in its maturing. 
synoum.—The aril of Synoum is in the form of a crescent- 
shaped fleshy mass in the sides of which the flat rather ircon- 
spicuous seeds are embedded. ‘This aril is probably a fusion of 
two arils, it is of a bright brick-red colour, and, as in the former 
case, probably aids in the dissemination of the seeds, through 
being eaten by birds. 
