238 RETIEWS. 



category we would just recall a difficulty wliicli constantly presents 

 itself when we contemplate this subject from — so far as we can ap- 

 prehend it — Mr. Darwin's point of view. If these plants be tending 

 to a diclinous condition, if such a condition advantage the species, 

 how and wliy did they ever become hermaphrodite ? We cannot 

 help conjecturing that there may be in plants two counter- agencies 

 at work, the one acting as a constant check upon the other ; the one 

 conservative, favouring the persistence of unaltered forms, indicated 

 in the general barreimess of hybrids and the difficulty of crossing 

 many nearly allied g|)ecies as well as in other and special arrange- 

 ments which we shall afterwards advert to, the other favouring, it 

 may be ever so slightly, a tendency to vary, indicated by the various 

 grades of diclinism, as also by special obstacles contrived absolutely 

 to prevent self- fertilisation in hermaphrodite flowers.* "While we 

 may, with perhaps the greater shew of reason suggest that certain 

 species are tendmg to a separation of the sexes, we must not forget 

 that arguments may be advanced to shew that it is not impossible 

 but that they may be striving towards more perfect hermaphroditism, 

 especially if we bring to mind the evidence (to which indeed we arc 

 scarcely hardy enough to attach a particle of weight) furnished by the 

 ' Greological Eecord.' This evidence does certainly appear in favour 

 of a greater predominance of unisexual forms at an early period than 

 obtains at the present day. A consideration of instances referred to 

 our second kind of dimorphism may perhaps enable us to appreciate 

 better the phenomenon, and further illustrate the remark that there 

 may possibly be two coimter agencies at work manifesting themselves 

 in various dimorphic conditions. 



Linnaeus in the ' Praelectiones Botanicae'f remarks of Viola mira- 

 hilisihsbt the eaz'ly flowers provided with a corolla are often barren, while 

 others appearing subsequently and destitute of a corolla are fertile. 

 This observation was extended by Gingins who published a Memoir 

 on the Violaceae in 1823. He shewed that violets presented the 

 singular peculiarity of producing imperfect flowers, more or less 

 destitute of petals, but with perfect fruits, which fruits he adds are 

 " quelquefois meme plus pai'faits que ceux qui succedent aus fleurs 

 completes." M. Monnier of Nancy, yet further extended our know- 

 ledge of this dimorphic condition in the violets. J He says of Viola 

 hirta that none of the early spring flowers yield fruit, " they all 

 abort and wither up ; " after the first flowering the leaves assume a 

 fuller development, they become more hairy and bear in their axils 

 flowers destitute of corolla and with the five stamens almost always 

 free and shorter than the ovary. The peduncles bearing these flowers 

 curve downward and bury the ovaries under the sut^face of the soil 

 where the seeds are ripened. M. Monnier found the sweet-scented 



* Conf. Hooker Introd. E.ssay to Tasmanian Fk)ra, x. 



t Ed. 1792, ].. 401. 



j Guilleniin's Archives dc Botanique, 1833, i. 412. 



