DIMORPHISM. 333 
Pteris quadriaurita, in which the fronds emerging from 
an adventitious bud are very different from the ordinary 
fronds. 
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PAT re 
Fig. 178.—Portion of a frond of Pteris quadriaurita, with an adventi- 
tious bud, the form of the constituent foliage of which is very different 
from that of the parent frond. 
Dimorphism—T'his term, applied specially to the 
varied form which the flowers or some of their con- 
stituent elements assume on the same plant, is an 
analogous phenomenon to what has been above spoken 
of as heterophylly, and, like it, it cannot, except under 
special circumstances, be considered as of teratological 
importance. A few illustrative cases, however, may 
here be cited. 
Sir George Mackenzie describes a variety of the 
potato’ (Solanwm tuberosum), which produces first double 
and sterile flowers, and subsequently single fertile ones ; 
the other portions of the plant do not differ much. 
1 * Gard. Chron.,’ 1845, p. 790. 
