180 REPRODUCTION IN PLANTS AND, ANIMALS. 



reticulated and blotched with white, and retains its ver- 

 dure through the winter. 



Among animals the majority of species, and among 

 plants the minority are unisexual, or dioecious ; that is to 

 say, the male and female organs of generation are on sepa- 

 rate individuals of the same species. 



Difference of sex is much more marked among animals 

 than among plants. Among insects the difference of sex 

 is readily perceived, not only by a difference in the organs 

 of generation, but by exterior characters which are easily 

 recognized. Thus, in general, the male is smaller than 

 the female; his antennae are longer and better formed; 

 very often his colors are more lively, his mandibles more 

 powerful, and he carries on his head or his thorax appen- 

 dages which are quite wanting in the female. The female 

 insect is sometimes apterous or provided with rudimentary 

 wings, whilst those of the male are fully developed. There 

 is no such marked difference between the sexes in dioe- 

 cious plants. The Ailanthus glandulosa may be adduced 

 as an illustration of this uniformity of appearance. With 

 the exception of its peculiar pollenic odor and the total 

 absence of pistils from its flowers, the male tree differs not 

 from the female in any other particular. The leaves of 

 both plants are precisely the same in configuration and 

 surface. The male and female trees are in fact so exactly 

 the same in appearance, that it is utterly impossible to re- 

 cognize the difference of sex, except at the epoch of flower- 

 ing. We are not aware of any dioecious plants which are 

 an exception to this law of uniformity, although doubtless 

 such exist in nature. 



Unisexual plants are apparently not so favorably situated 

 for sexual intercourse as the hermaphrodite species, where 

 the male and female organs are present in the same flower. 



