unimpregnated Ovulum in Phenogamous Plants. 357 
_ always agreéd in direction with the nucleus. And lastly, that 
at the apex of the nucleus the radicle of the future Embryo 
would constantly be found. 
On these grounds my opinion respecting the Embryo of Ce- 
phalotus was formed. In describing the Ovulum in this genus, 
I employed indeed, the less correct term “‘sacculus,” which, 
however, sufficiently expressed the appearance of the included 
body in the specimens examined, and served to denote my un- 
certainty in this case as to the presence of the inner membrane. 
I was at that time also aware of the existence, in several 
plants, of a foramen in the coats of the Ovulum, always distinct 
from, and in some cases diametrically opposite to, the external 
umbilicus, and which I had in no instance found cohering 
either directly with the parietes of the Ovarium, or with any 
process derived from them. But, as I was then unable to de- 
tect this foramen in many of the plants which I had examined, 
I did not attach sufficient importance to it; and in judging of 
the direction of the Embryo, entirely depended on ascertain- 
ing the apex of the nucleus, either directly by dissection, or 
indirectly from the vascular cord of the outer membrane: the 
termination of this cord affording a sure indication of the ori- 
gin of the inner membrane, and consequently of the base of 
the nucleus, the position of whose apex is therefore readily de- 
termined. 
In this state of my knowledge the subject was taken up, in 
1818, by my lamented friend the late Mr. Thomas Smith, who, 
eminently qualified for an investigation where minute accuracy 
and great experience in microscopical observation were neces- 
sary, succeeded in ascertaining the very general existence of 
the foramen in the membranes of the Ovulum. But as the fo- 
ramina in these membranes invariably correspond both with 
each other and with the apex of the nucleus, a test of the di- 
rection of the future Embryo was consequently found nearly 
as universal, and more obvious than that which I had pre- 
viously employed. 
To determine in what degree this account of the vegetable 
Ovulum differs from those hitherto given, and in some measure 
that its correctness may be judged of, I shall proceed to state 
the various observations that have been actually made, and 
the opinions that have been formed on the subject, as briefly 
as I am able, taking them in chronological order. 
In 1672, Grew* describes in the outer coat of the seeds of 
many Leguminous plants a small foramen, placed opposite to 
the radicle of the Embryo, which, he adds, is ‘not a hole ca- 
sually made, or by the breaking off of the stalk,” but formed for 
* Anatomy of Veget. begun p. 3, Anat. of Plants, p. 2. 
purposes 
