Anderson • Cytotaxonomy 



breeding. I'lirthcrinore, it was virtuall\- 

 identical with a primitive hexaploid 

 wheat, known as spelt, which has been 

 a minor European crop since Roman 

 times. The spelt artificially produced 

 by McFadden and Sears is fertile with 

 European spelt and that the latter is a 

 pohploid of Aegilops squarrosa and 

 some simpler wheat may be taken as 

 proved. 



Onlv one thoroughly familiar with 

 the literature on the histor)- of wheat 

 can realize how completely the work 

 of McFadden and Sears causes a re- 

 alignment of the facts and theories in 

 that complicated field. 



We now learn that our commonest 

 wheats belong to the genera Agropyron 

 and Aegilops quite as much as they do 

 to the genus Triticum. Were it possible 

 to sacrifice convenience to accuracy, 

 our bread wheats could more fiittingly 

 be designated as Aegilotriticopyron 

 sativum than as the currently accepted 

 Triticum sativum. McFadden even 

 thinks it likely that a fourth genus, 

 Haynaldia, by simple hybridization 

 without any polyploid realignments, 

 mav have contributed some of the dis- 

 tinctive characteristics of our tetraploid 

 macaroni wheats. Haynaldia, growing 

 as a weed in primitive grainfields, 

 might well have crossed with some of 

 the wheats. These hybrids, crossing 

 back to the wheats again, would bring 

 a little Haynaldia germ plasm into the 

 wheats. In other words, we now realize 

 that if we are to understand the wheats 

 of the world, either as a key to pre- 

 history or as the staff of life for a good 

 portion of the human race, we must 

 study a whole group of quack grasses 

 and other weeds from the Near East 

 and Asia. For the purpose of practical 

 plant breeding the world now finds 

 itself needing to know in detail about 

 several humble weeds, plants so far 

 removed from our ordinary lives that 

 we have no common English names 



243 



for them and must resort to such un- 

 wieldy technical vocables as Agropyron, 

 Haynaldia, and Aegilops in discussing 

 them! 



This example by no means exhausts 

 the new evidence that has been turned 

 up by the cytologists in the last few 

 decades concerning the origins of cul- 

 tivated plants. There are new facts and 

 new insights into the origin of to- 

 baccos, of white potatoes, of citrus 

 fruits, of bluegrasses, of apples and 

 pears, of roses, chrysanthemums, dahl- 

 ias, and many other ornamentals, and 

 of such modern domesticates as blue- 

 berries and strawberries. But quite as 

 important as any of the specific infor- 

 mation which it contributes to the 

 problem of the origin of cotton or the 

 origin of tobacco, is the bearing of the 

 cytological evidence on the general 

 problem of cultivated plants as a 

 whole. 



In the first place it gixes us a wholh' 

 new appreciation of the importance of 

 hybridization. After reviewing the 

 cytological and breeding evidence, hy- 

 bridization seems to have been a really 

 major factor in establishing our crop 

 plants. Fifty years ago an\' scientist 

 who would have dared to suggest that 

 our common wheats are quack grasses 

 quite as much as they are wheats, or 

 that seedless bananas could only be 

 produced by crossing certain kinds of 

 wild, seedy bananas, would not have 

 been taken seriously. Tlie modern plant 

 breeder not only makes such sugges- 

 tions, he goes ahead and proves them. 

 The fortunate thing for our under- 

 standing is the way in which poly- 

 ploidy preserves for centuries clear 

 c\tological evidence of certain hybridi- 

 zations. The whole set of chromosomes 

 is still there and with luck and per- 

 severance it may be identified, even 

 though the original cross took place 

 in the Iron Age or earlier. Without 

 polyploidy this clear evidence would 



