52 МВ. J. MIERS ON THE ВАВВГУСТОМ1АСЕХ. 
plumule perforating the thin coating of the exorhiza, and protruding from it in the form 
of a collet, bearing 2 very small lobes; this is done while it is confined within its entire 
integument; but the growth is of short duration, being arrested by the strong resistance 
of the bony nut, while the inward pressure causes the exorhiza to become moulded into 
the channel in which the plumule lies. Тһе lobes just mentioned were regarded by 
Gaertner as cotyledons; and so they have been universally considered; but any one who 
will reflect for a moment must see that they are, in fact, the plumule; for Gaertner says 
he could discern no other, and his expression “plumula nulla" is an obvious incon- 
sistency. 
We may obtain, by means of analogy, some additional light by comparing the embryo 
of Butonica with that of Rhizophora, which germinates also within the pericarp. There 
the ovary is 3-celled, with several ovules; but the fruit, by abortion, is 1-celled and 
monospermous; the pericarp is oblong, about 1 inch long, coriaceous, partly inferior, 
mostly superior, terminated by a bifid style, and surrounded above its base by the per- 
sistent calyx ; the seed which fills its cavity is invested. by a thin integument, has no 
albumen, and an embryo of singular development, consisting of an external exorhiza 
and an internal neorhiza. The latter, while upon the tree, begins to swell, and forces its 
way through the integument and through the pericarp, by rupturing a small hole between 
the lobes of the style, and it grows to a length of 10 inches by the time that the exorhiza 
has only extended half an inch beyond the pericarp. This exorhiza is 1 line thick, is of a 
greenish hue, and is filled with soft threads, probably oil-cells, such as I described in the 
embryo of Clusia, its upper extremity being lacerated by the protrusion of the neorhiza, 
while at its base, within the calyx, it is terminated by a hollow dome of soft yellow con- 
sistence, containing no threads; except in this part, it is confluent with the basal portion 
of the neorhiza, but is free from it at the dome, which encloses the free plumule that 
terminates the end of the neorhiza and consists of 4 or 6 small leaflets plicated, con- 
voluted, and converging to a point. This dome-shaped portion is called the calyptra 
by Jacquin, the albwmen by Gaertner! ; the exorhiza is the erus of J acquin, the vitel/us of 
Gaertner; the neorhiza is the semen of J acquin, the radicula of Gaertner; while the ter- 
minal free end of the neorhiza is the conus of Jacquin, and the cotyledons of Gaertner. 
Jacquin gives a long account of its germination and subsequent growth. The semen 
(neorhiza) becomes the trunk of the new plant; the tubercles on its surface throw out 
numerous rootlets that form, ultimately, arched buttresses for its support on the sea-bed 
beneath it; while, at the other extremity, as soon as it can detach itself from the peri- 
carp, the plumule expands into an ascending stem, crowned by permanent real leaves. 
In this development. the exorhiza seems to perform no other part than to afford its nou- 
rishing juices to the young plant; and it gradually withers, as in Clusia; the medullary 
sheath coating the neorhiza quickly generates a system of woody vessels, so hard as to 
render it difficult. to be cut by a knife, the neorhiza being contracted into a narrow | 
central pith,—a structure confirmed by the observations of Griffith ; the embryo may be 
said to be coleorhized by the concealment of the plumule within the terminal dome, 
* Griffith (Notule, iv. 664) calls this cotyledon. | 
