160 PRIMITIVE FORMS OF LIFE 



seem at first sight as though this rule did not apply to plants, 

 as each flower is hermaphrodite, but it must not be forgotten 

 that in plants the primordial individual element is the leaf, 

 so that a vascular plant is best considered as a collection of 

 leaves. In the flower, however, the fertile leaves are exclusively 

 male (stamens) or female (carpels), and consequently unisexual. 

 We should also remember that in the oldest flowering plants 

 the male flowers generally grow on different branches from the 

 female flowers. Both are made up of cones or catkins exclusively 

 male or female, and the sexuality frequently extends to the 

 whole plant, in which case it is said to be dioecious (p. 103). 



Throughout the Animal Kingdom the males or females share 

 distinctly the characteristics of the sexual elements they 

 produce. The females of the species belonging to the same 

 genealogical stock generally resemble each other considerably, 

 and retain the forms and colours that are practically those of 

 the young individuals of the species, which indicates both that 

 they have a common origin and that they have evolved but 

 little. They are larger than the males, very often some- 

 what inactive, and usually accumulate more reserve substances 

 in their tissues. The males, on the contrary, use up the products 

 of their alimentation in activity. They are vividly coloured. 

 Ornaments of all kinds, horns, tusks, manes, plumes of 

 feathers, and aigrettes embellish the primitive form conserved 

 by the females. Sometimes they produce substances with special 

 odours. Through heredity, these acquired characters are often 

 passed on to the females. Thus the small blue butterflies of 

 our fields, called Argus, have generally brown females with 

 yellow spots ; but in some species the blue colour of the 

 male can extend to the female. Again, among the Kingfishers 

 the females of the Halcyon are grey, while the males 

 have those magnificent blue and tawny shades which in our 

 ordinary species are common to both sexes. 



The incapacity of the males to provide themselves with 

 reserve nourishment has a fatal result for them in those groups 

 of the Animal Kingdom which do not endow the organism with 

 much power of resistance. Already among many Insects 1 their 

 span of life is short ; they do not concern themselves at 

 all to provide for the future of their young, and die as soon as 

 they have fulfilled their sole function of fertilization. Others 



1 Bees, Wasps, Ants, and many Flies with four wings or Hymenoptera. 



