CHAP. II. 
OVULE. 
•215 
lotropous. In both these modifications, the base of the ovule 
and the base of the nucleus are the same. 
In a third class the axis of the ovule remains rectilinear ; 
but one of the sides grows rapidly, while the opposite side 
does not grow at all, so that the point of the ovule is gradually 
pushed round to the base; while the base of the nucleus is 
removed from the hilum to the opposite extremity (Plate V. 
fig. 16 — 21.) : and when this process is completed the whole of 
the inside of the ovule is reversed ; so that the apex of the 
nucleus, and consequently the foramen, correspond with the 
base of the ovule. Such ovules as these Mirbel terms ana- 
tropous ; they are very common : examples may be found in 
the Almond, the Apple, the Ranunculus, the Cucumber, &c. 
When the base of the nucleus is thus removed from the base 
of the ovule, a communication between the two is always 
maintained by means of a vascular cord, called the raphe 
(Plate V. fig. 24. e, 25./*). This raphe, which originates in 
the placenta, runs up one side of the ovule, until it reaches 
the base of the nucleus : and there it expands into a sort of 
vascular disk, which is called the chalaza (Plate V. fig. 2A.f. 
25. g). As the chalaza is uniformly at the base of the 
nucleus, it will follow that, in orthotropous and campylotro- 
pous ovules, it is confounded with the hilum ; while it is only 
distinguished in anatropous ones, in which alone it is dis- 
tinctly to be recognised. 
In addition to these there is the amphitropous ovule, whose 
foraminal and chalazal ends are transverse with respect to the 
hilum, which is connected with the latter by a short raphe ; 
and the semianatropous^ which is only different from the last, 
in the ovule being parallel with the funiculus instead of being 
at right angles with it. 
The following figures give a comparative plan of these 
ovules. 
135 
d & 
a, Orthotropous, or atropous ; b, campylotropous ; c, anatropous ; d, amphitropous ; e, semi- 
anatropous. In these figures * represents the chalaza, and - the foramen. 
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