IN FLOWERING PLANTS. 181 
According to this author, all ovula are originally orthotro- 
: pous; that is, the opening of the teguments, and consequently 
the apex of the nucleus is directly opposed to the base 
of the ovule as indicated by its point of attachment to the 
placenta, either directly, or more frequently, indirectly. 
n many cases this correspondence continues in the ripe 
seed, no change whatever having taken place ; and such form 
what M. Mirbel calls antitropous ovula. 
In all others a change does take place. In one modifi- 
cation, the change is accomplished by a mere curvature, 
which causes the apex of the ovulum to be approximated to 
the base, or point of attachment. Such constitutes M. Mirbel's 
campylotropous ovule. 
In others again, change is effected by an actual change of 
position in the base of the nucleus, now no longer cor- 
responding to the point of attachment of the ovulum. This 
forms M. Mirbel’s anatropous ovule, and it is the most fre- 
quent form. 
M. Mirbel has proposed another class ; which he calls 
amphitropous, and which differs only from the anatropous 
form in the shortness of the raphe, from which it results that 
the chalaza is lateral with respect to the geometrical apex of 
the seed. The distinction is, I think, needless, since the 
chalaza still corresponds to the base of the nucleus. 
M. Brongniart, at p. 72, notices another modification, in 
which without any curvation, or un repliement réel, in the 
membranes of the ovulum, the foramen is approximated to the 
hilum, as in Chenopodes, Amarantacee, etc. 
M. Mirbel has well shown that anatropism is not necessa- 
rily dependent upon a change of position, for he has shewn 
satisfactorily that in a few instances it results from unequal 
growth. 
See his observation on Quercus, Alnus, Corylus ; Memoire 
p. 45, 
And on Primulacez, and Plantaginee, p. 47, pl. 10. 
These anomalies are curious and well worth notice, as 
they perhaps give rise to all those forms of anatropism, in 
which there is no trace of a raphe visible. 

