64 SOUTH AFRICAN FLOWERING PLANTS, 



these two words, Species and Genus, for they lie at the 

 root of all classification. He is familiar with the fact 

 that there is an immense number of different kinds of 

 Heath. Without being a botanist he recognizes that 

 there is a strong likeness among them. They constitute 

 a genus, but each of the different kinds is a species. 

 There are many South African genera besides the 

 Heath, which have a large number of species, as 

 Aspal'atJms {Leguminosce), Morce'a {Iridece), Di'sa 

 (Orchid ece)} 



The question is, how must we distinguish one 

 species from another ? It is not enough to do so by a 

 single, two, or very few features, but they must be com- 

 pared throughout the entire plant, and then each 

 species will be known by a collection of constant ^ 

 features called their " specific characters." 



How do these differences arise ? The answer is 

 that all plants possess " variability " or the power to 

 change; and this power is brought into action by 

 changes in the external conditions of the plant ; so 

 that when the seeds of any plant get transplanted by 

 wind, birds, etc., to a distance where the soil and 

 atmosphere are different, the seeds germinate, but grow 

 up slightly different from the parent, and more in 

 harmony with the new conditions ; the next generation 

 carries on the " adaptation ; " then, after a few years, the 



' See these families for figures, 

 * I.e. by heredity. 



