Unisexual Crosses 265 



the ordinary lucerne. It always comes true 

 from seed and may be seen in a wild state in 

 parks and on lawns. It is one of the oldest 

 hybrids with a pure and known lineage. The 

 original cross has been repeated by Urban, who 

 found the hybrid race to be constant from the 

 beginning. 



Another very notorious constant hybrid race 

 is the Aegilops speltaeformis. It has been 

 cultivated in botanic gardens for more than 

 half a century, mostly in annual or biennial 

 generations. It is sufficiently fertile and al- 

 ways comes true. Numerous records have 

 been made of it, since formerly it was believed 

 by Fabre and others, to be a spontaneous transi- 

 tion from some wild species of grass to the ordi- 

 nary wheat, not a cross. Godron, however, 

 showed that it can be produced artificially, and 

 how it has probably sprung into existence 

 wherever it is found wild. The hybrid between 

 Aegilops ovata, a small weed, and the common 

 wheat is of itself sterile, producing no good pol- 

 len. But it may be fertilized by the pollen of 

 wheat and then gives rise to a secondary 

 hybrid, which is no other than the Aegilops 

 speltaeformis. This remained constant in God- 

 ron 's experiments during the first few genera- 

 tions, and was at that time identical with its 

 present form. 



