Nov. 12, 1921 Genetic Behavior of Spelt Form in Crosses 337 



Some wheats exhibit some of the spelt characters in a very weak form. 

 For instance, some are more or less strongly keeled or have a flat shoulder 

 at the distal part of the glume. While such wheats are classified as 

 T. sativum, they are not true sativum in the sense used here. They do 

 not represent the type. 



Aside from the glumes, these species have other distinguishing char- 

 acters. Of these, the brittleness of the rachis and nonshattering qualities 

 of the spikelet in spelt may be mentioned as contrasted with the sativum 

 types, the latter being nonbrittle and shattering easily. 



Although the heads of the spelt varieties commonly grown at experi- 

 ment stations in this country usually are lax, laxness of the head is not 

 necessarily a characteristic of the spelt. Compactness may easily be 

 introduced into spelts when crossed with T. compactum, which is really 

 only a wheat carrying a genetic factor or factors for compactness. 



The characters differentiating these two species are recapitulated 

 below. This list includes also some other minor characters. 



T. sativum. T. spclta. 



Outer glumes — Outer glumes — 



Weakly attached by narrow base. Firmly attached by wide base. 



Weakly keeled. Strongly keeled. 



Apex tapering. Apex blunt. 



Depression or wrinkle near point of at- No wrinkle near base. 



tachment. 



Veins not prominent. Prominent parallel longitudinal 



veins. 



Shoulder narrow to broad, with no Shoulder broad, with two or three 



dentation. dentations. 



Glume soft. Glume, lemma, and palea firm and 



thick. 



Spikelets — Spikelets — 



Kernel loosely held between glumes Kernel tightly held (nonshattering). 



(shattering). 



Spikelets spreading somewhat from Spikelets oppressed tightly against 



rachis. the rachis. 



Usually three or more kernels per Usually two and rarely three kernels 



spikelet. per spikelet. 



Rachis — Rachis — 



Tenacious. Fragile. 



There also are differences in the shape of the kernels of these two 

 species (i).^ 



LINKAGE OF SPECIFIC CHARACTERS 



In order to understand the manner in which these two forms are here 

 classified, it is necessary to refer to the linkage of their specific characters, 

 without discussing the details. 



Most of the characters tabulated above show two limits of contrasts. 

 When a wheat is crossed with a spelt, a gradation of forms naturally 



' Reference is made by rmmber (italic) to " Literature cited," p. 363-364. 



