250 Fertilisation and Hybridisation 



be useless. Nevertheless it has been retained and its 

 meaning has been gradually limited. Especially in de- 

 scribing horticultural plants the conception is sufficiently 

 restricted by excluding on the one hand the hybrids, on 

 the other hand the improved races obtained by selection, 

 and finally the so-called elementary species that, taken 

 together, form our ordinary species. 



Upon reviewing the cases that are left, two types can 

 be plainly distinguished, the constant and the inconstant 

 varieties. The former are not inferior to true species in 

 point of constancy. Their characters vary, in the single 

 individuals, around a mean, but in the main not more so 

 than the corresponding characteristic of the species. 

 From this they are separated by a decided chasm. In 

 pure fertilization they never bridge this chasm, or at 

 least, extremely rarely, but in crossing they revert very 

 easily to the species. It is this very reversion that stamps 

 them varieties, and when the crossing is not artificial but 

 natural, brought about by insects, it escapes observation, 

 and only the fact of the reversion strikes the gardener. 



These constant varieties are, as a rule, distinguished 

 from the species to which they belong, by lacking some 

 striking quality that adorns the latter. Most frequently 

 it is the coloring of the flower or, in the case of flowers 

 with combined colors, as in the yellow and red tulips, one 

 of the individual colors, that is wanting. Often they 

 lack hairs or thorns, very frequently the development of 

 the blade is arrested, and split leaves originate. In all of 

 these cases there is no ground for the opinion that the 

 failure of the visible character means also the loss of the 

 respective unit. Rather does everything point to the 

 fact that the unit has simply become inactive, that it is in 

 a state of rest, or as it is usually expressed, that it has be- 



