Chap. XV. OCCASIONALLY INTERCROSSING. G9 



respect to the common pea, I have ascertained that it is 

 rarely crossed in this conntr}'' owing to premature fertilis- 

 ation. There exist, however, some plants which under their 

 natural conditions ap})ear to be always self-fertili^jed, buch as 

 the Bee Ophrys {Ophrys apifera) 2indi a few other Orchids; 

 yet these plants exhibit the plainest adaptations for cross- 

 fertilisation. Again, some few plants are believed to produce 

 only closed flowers, called cleistogene, which cannot j)ossibly 

 be crossed. This was long thought to be the case with the 

 Leersia oryzoides,^'^ but this grass is now known occasionally 

 to produce perfect flowers, which set seed. 



Although some plants, both indigenous and naturalised, 

 rarely or never produce flowers, or if they flower never 

 produce seeds, yet no one doubts that phanerogamic plants 

 are adapted to produce flowers, and the flowers to produce 

 seed. When the}'' fail, we believe that such plants under 

 different conditions would perform their proper function, or 

 that they formerly did so, and will do so again. On analo- 

 gous grounds, I believe that the flowers in the above specified 

 anomalous cases which do not now intercross, either would 

 do so occasionally under different conditions, or that they 

 formerly did so — the means for affecting this being generally 

 still retained — and will again intercross at some future 

 period, unless indeed they become extinct. On this view 

 alone, many points in the structure and action of the repro- 

 ductive organs in hermaphrodite plants and animals are in- 

 telligible, — for instance, the fact of the male and female organs 

 never being so completely enclosed as to render access from 

 without impossible. Hence we may conclude that the most 

 important of all the means for giving uniformity to the in- 

 dividuals of the same species, namely, the capacity of oc- 

 casionally intercrossing, is present, or has been formerly 

 present, with all organic beings, except, perhaps, some of 

 the lowest. 



On certain Characters not blending. — When two breeds are crossed 

 their characters usually become intimately fused together; but 



" Duval Jouve, ' Bull. Soc. Bnt. setting seed, see Dr. Ascherson in ' Bot. 

 de France,' torn, x., 1863, p. 194. Zeitung,' 1864, p. 350. 

 With respect to the perfect flowers 



