CHAP. III. 
SYMMETRY. 
303 
developement of the posterior stamens and sepals ; and in 
Leguminosae, in which the posterior petal overbalances those 
in front, the anterior sepals and stamens restore the equi- 
poise. If in Goldfussia it is the right hand-leaf of one pair 
which is the smaller, it is the left leaf of the next pair. 
In the arrangement of the organs round the axis of a 
plant, the same careful provision of antagonistic developement 
is manifest. If one leaf grows on the right of a stem, the 
next appears on the left, the next on the right ; if a pair of 
opposite leaves points N. and S., the next pair points E. and 
W., the next N. and S. again ; and, if a whorl of 4 leaves is 
directed to the cardinal points, the next whorl is directed to 
the intermediate points of the compass, and so on. The same 
laws will be found to be observed, with little variation, through 
all the organs of a flower. 
Messrs. Chatin and Moquin Tandon- have been led, by 
such considerations as these, to assume that there are in the 
vegetable, as in the animal, kingdom, both a centripetal and 
centrifugal force of developement ; the former appertaining 
to Exogens and Endogens, and the latter to Acrogens. I 
know nothing of the evidence upon which M. Chatin thinks 
this proposition may be maintained. M. Moquin Tandon has, 
however, given a sketch of his ideas upon the same subject, 
and I must confess they do not appear to me conclusive. (See 
Comptes rendus, v. 691.) 
