54 Immunity in Cereah 



fuliginosmn M? — a variety with black bearded hairy (;ars and led 

 grains — yet this form is distinguished by uiany other characters from 

 all our races of Tr. vulgare, which are not inehided in the chissification 

 of Koemicke. 



The straw of this wheat is relatively full of pith. TTsually, the varieties 

 of Tr. vulgare have a hollow straw. The stem-knots of this wheat are 

 visibly hairy; generally they are smooth in the species Tr. vulgare- 

 The rachis of " Persian Wheat " is only half as broad as in common 

 wheats. Ordinarily in wheat, only flowering glumes possess an awn. 

 In this " Persian Wheat," the empty glumes are also awned'. Besides 

 these, there are other small inorpholugical differences in the structure 

 of ear and leaf. 



By crossing this wheat with other varieties of Tr. vulgare, it was 

 observed that the percentage of successful results was \ er^' small. The 

 same fact was repeated the next year. Usually in the same conditions 

 the percentage of success in our crossings of different varieties of Tr. 

 vulgare was very high. In the Ft hybrids ($ "Persian Wheat" x (/ Tr. 

 vulgare var. lutescens Kcke.) about 70 ^ of the spikelets were sterile. 



Finally in some of our crossings of susceptible races of wheat with 

 immune ones, the susceptibility to mildew was clearly dominant, and 

 F^ hybrids were severely attacked by this fungus, as was seen in the 

 experiments of Prof Biffen with barley. But in the case of crossing 

 "Persian Wheat" with a very susceptible race (Tr. vulgare var. lutescens 

 Kcke.), only after many efforts did we succeed in infecting slightly the 

 F^ hj'brids, when in the same conditions the susceptible parent was 

 severely attacked. In other words immunity in this instance is not 

 " recessive." 



\yithout dwelling further on this case, we must remark only that 

 all that has just been said about this wheat allows a systematist to 

 separate it from other varieties of Tr. vulgare, and makes it of special 

 interest for the genetist. 



An instance I came across in the investigation of barley is analogous 

 to that described by Prof. Klebahn with willows. In our collection we 

 had some samples of naked two-rowed barley from different parts of 

 Ru-ssia. In the classification of Koernicke (1885), which we made use 



' Tlie name Tr. i-ulgare var. fuliginosum Al. is a collective name. We know quite 

 ordinary susceptible wheats of the species Tr. vulgare which have black, hairy, bearded 

 ears with red grains, like "Persian Wheat," and which must be placed in Koeruicke's 

 classification under the name " var. /H/((/(«oj>»»t. " 



-' This character is observable also in a few races of Tr. vuhjarv, belonging to different 

 varieties, which are cultivated in Asiatic Russia and Persia. 



