MR. J. MIERS ON THE BARRINGTONIACE.E. 51 
the seed of Xanthochymus in germination’. I had not then witnessed the fact myself ; 
but not long afterwards Dr. Spruce kindly sent me the seeds of a Clusia which he 
gathered in the act of germination and in its several stages of growth. Неге the central 
body I had described became much broader below, and had forced its way through the 
apical lobes I had figured, rising in a naked subulate form, till it had grown to 10 times 
the length of the outer body, which had not enlarged in any way, but which, on the 
contrary, had withered into a mere membrane, after yielding its substance to nourish 
the growing portion. Хо scales were visible on the rising shoot; but when it had 
reached the height above mentioned, it threw out at its summit at first two, and then other 
decussating pairs of broad rounded leaflets; and at the bottom of the seed a distinct 
rootlet was evolved. This agrees perfectly with the figure of Roxburgh; only there were 
no scales, and no appearance of а second root close to the plumule. Тһе specimens of 
the Clusia-seeds are. now before me; so that 1 can vouch for the correctness of this 
description. 
From this we may gather the important fact that the outer body of the embryo forms 
here no portion of the new plant, and that its use appears only to perform the part of а 
cotyledon, in affording nourishment to the inner growing portion. It is probable that 
the same occurs in the germination of the large fleshy embryo in Butonica, which Rox- 
burgh figured as growing in the same manner?; but we have no evidence to show 
what becomes of the outer exorhizal portion in those cases, or that it forms any part 
of the new plant. This would lead to the conclusion that in Butonica the exorhiza 
is simply a cotyledon under a sheathing form, analogous to the radicle of an ordinary 
dicotyledonous seed from which the cotyledons have have been eut away, leaving a 
cylinder consisting of an outer sheath confluent round an inner body, terminated by the 
plumule. An example somewhat similar is figured by Gaertner in Hippocastanwin *, 
with this distinction, that the plumule is there coleorhized, a very rare circumstance in 
seeds eminently dicotyledonous. 
One important point of structure was noticed by Dr. Thomson in the речин of Buto- 
nica: in а section of it, under the microscope, he found that both the exorhiza and 
neorhiza are alike formed of simple cellular tissue and starch granules, but that between 
them, adhering to both, there exists a distinct layer of delicate vessels, continuous up- 
wards and downwards with the ligneo-vascular cylinder of the stem and root*. This, 
without doubt, is the medullary sheath described by Mirbel®, investing the cellular 
tissue of the axis of the plumular support, and forming there all the vessels which con- 
stitute the wood and bark in the new plant. : 
. А very instructive example of the kind of embryo іп Butonica occurs in that of 
Caryocar, which has a gigantic amygdaloid neorhiza, surrounded by a rather thin exorhiza 
of uniform thickness; the former is of a crescent form, in the upper horn of which is 
observed the radicular point, and in the lower horn the plumular extremity. The 
germination commences within the pore» ‘аз soon as the seed is formed, by the 
' Linn. Trans. xxi. tab. 26, fig. 34. 2 Wight, Icon clii. fig. 5, and Roxb. Flor. Ind. ii. 635. 
* De Fruct. ii, 135, tab. 111. fig. б, Н. 4 Journ. Proc. Linn. Soe. ii. pp. 51, 52. 5 Elém. i. 114. 
