338 ARILLUS.—CARUNCULE. 
name of arillus or aril has been given. No trace of this structure 
is present in the ovule till after the process of fertilisation has 
taken place. Two kinds of aril have been described, which 
have been respectively called the true arillus, and the false 
arillus or arillode. These have an entirely different origin ; 
thus, the true arillus arises in a somewhat similar manner to 
the coats of the ovule already described (page 329), that is to 
say, it makes its first appearance around the hilum in the form 
of an annular process derived from the placenta or funiculus, 
and gradually proceeds upwards, so as to produce a more or less 
complete additional covering to the seed, on the outside of the 
testa. This arillus is well seen in the Nymphcea (fig. 757, A, A). 
But the false arillus or arillode arises from the micropyle, and 
seems to be a development or expansion of the exostome, 
which gradually extends itself more or less over the testa to 
which it forms a covering, and after thus coating the seed, it 
Fic. 758. 
Fig. 758. Progressive development of the arillode in the seed of the Spindle- 
tree (Euonymus). a. Arillode. f. Funiculus. 1, represents the youngest 
seed; 2 and 3, the progressive development of the arillode; 4, the oldest 
and fully developed seed. 
may be even bent back again so as to enclose the micropyle. 
The gradual development of the arillode in the seed of the 
Spindle-tree is well shown in jig. 758. In the Nutmeg, the 
arillus originates from both the hilum and the micropyle ; it 
forms a scarlet covering to the testa, and is commonly known 
in commerce when dried and preserved, under the name of 
mace. According to Miers, the arillode in the Spindle-tree is 
produced from the funiculus and not from the exostome, in 
which case it would necessarily be an arillus, and not an arillode 
as commonly described. In practical Botany both the true 
arillus and arillode are commonly designated under the general 
term of aril. 
Caruncules or Strophioles.—These are small irregular protu- 
berances which are found on various parts of the testa. They 
are always developed, like the arillus and arillode, subsequent 
to fertilisation, and are accordingly not found in the ovule. In 
the Milkwort (jig. 759) they are situated at the base or hilum 
of the seed ; in the Asarabacca (jig. 760) and Violet on the side, 
