246 
CONTRIBUTIONS TO BOTANY. 
brane be a true arillus, as our materials are not sufficient for the 
complete investigation of its nature. Although marked with 
what seems like a raphe, it cannot be the testa or any proper 
integument of the seed, as Fenzl (in PI. Hugel) took it to be, 
for it has no connexion with the corneous seed-coat at the cha- 
laza, but only at the hilum; the chalazal end appears to be 
slightly open, as would be the case with an arillus : perhaps this 
membrane is a separable lining of the coccus.” 
I have not been able to detect the presence of any kind of 
vessels in this tunic, particularly in the prominent line that 
seems like a raphe,” and which Endlicher positively calls a 
raphe : this prominence appears to me nothing more than a mere 
impression of the sutural line of the coccus, and is a common 
feature seen upon the corneous coating of the seed in the Col- 
letiece and other Rhamnaceous genera. The tunic certainly pre- 
sents aU the characters of an arillus ; and, as Dr. Asa Gray 
justly remarks, it cannot be one of the proper integuments of 
the seed. The hard seed of Alphitonia is perfectly sessile within 
it, and is attached to it by a small open transverse fissure in its 
base, as in Zizyphus. 
Other circumstances, however, present themselves in the or- 
ganization which I have found in the seed of Alphitonia excelsa, 
that are worthy of record, as they completely confirm all the 
details of structure previously described, and which seem to 
prevail throughout the Rhamnacea. The second hard tunic, 
which lies within the outer brittle coating last described, becomes 
softened by maceration, when it is easily detached ; it is then 
very lax, is of a pale-brown or yellowish colour, quite homoge- 
neous in texture, void of any vessels, and encloses an oval body 
covered by a thfid tunic, which is notably smaller in size, and 
therefore leaves a considerable vacant space all round its sides 
and its summit, and is connected with the second tunic only at 
a small point in the base, which corresponds with the basal slit 
in the outer tunic of Colletia and Zizyphus. The summit of this 
third tunic is marked by a large tumid spot, evidently a chalaza, 
which exhibits no indication of any previous connexion with the 
second tunic; along each margin, emanating from the basal 
point of attachment, and crossing over the chalaza, there is seen 
a prominent white cord, filled with spiral vessels, which is im- 
bedded in the fleshy tissue of the integument, in one continuous 
and completely peripherical line, exactly like that described in 
Colletia and Zizyphus. Within this tunic is yet a fourth, 
delicate integument, a thin albumen, and an embryo similar in 
form to that of 'Colletia *. 
* The details of structure of the ovule and seed of Alphitonia are 
shown in Plate 33 f. 
