Unisexual Crosses 275 



psittacinus and G. cardinalis, and between their 

 hybrid, which is still known under the name of 

 Gandavensis and the purpurea-auratus. But 

 other authors give other lines of descent. So 

 it is with Amaryllis, which is said by De Graaff 

 to owe its stripes to A. vittata, its fine form to 

 A. Brasiliensis, the large petals to A. psittacina, 

 the giant flowers to A. Leopoldi, and the piebald 

 patterns to A. pardina. But here, too, other 

 authors give other derivations. 



Summarizing the results of our inquiry we 

 see in the first place how very much remains to 

 be done. Many old crosses must be repeated 

 and studied anew, taking care of the purity of 

 the cross as well as of the harvesting of the 

 seeds. Many supposed facts will be shown to 

 be of doubtful validity. New facts have to be 

 gathered, and in doing so the distinction be- 

 tween specific and varietal marks must be taken 

 strictly into account. The first have originated 

 as progressive mutations; they give unisexual 

 crosses with a constant offspring, as far as ex- 

 perience now goes. The second are chiefly due 

 to retrograde modifications, and will be the sub- 

 ject of the next lecture. 



