52 Immunitjj in Cereals 



Working both on the imniunity an() systeniatics of cereals, I often 

 had an opportunity of proving the connection between the relationship 

 and fungal reactions of these plants. My observations led me to the 

 conclusion that fungi, as a physiological test, may be very useful in 

 the genetic and systematic study of this plant gi-oup. 



Some of the results obtained have been published (16). Here I 

 propose to cite several general conclusions from work done, and then 

 add new data. 



To begin with, a few words about the application of fungal tests 

 for the purposes of the systematics of cereals. At the present time 

 attention, in the systematic study of these plants, is being directed 

 towards numerous small constant botanical units, the so-called " races." 

 The principal justification of this work is a very real need for the 

 drawing up of a detailed catalogue of cereal races, useful alike to 

 the worker in genetics and to the practical agriculturist. In the 

 description of these races not only morphological characters are taken 

 into account, as is usual in purely systematic studies, but also physio- 

 logical ones. 



The extremely narrow specialization of many fungi found on cereals, 

 and the well-known fact of the existence of differences in the degree of 

 susceptibility to diseases amongst various sorts of them, waiTanted 

 first of all the attempt to use fungal tests for the recognition of the 

 races. 



In fact, by the aid of this method, I was easily able to divide many 

 varieties' of wheat and oats into races. The important role in the 

 systematic study of such a character as the degree of immunity is 

 increased, as practice in its application has shown, by the circumstance 

 that the physiological individualisation of race is very often accom- 

 panied by morphological characters which, however, are externally not 

 very conspicuous. In these cases the peculiarity in behaviour towards 

 fungi obliges the observer to pay more attention to this or that pre- 

 viously unsuspected race, and in the end he usually succeeds in finding 

 in it some other confirmatory differences". 



1 We use here the word " variety " in a purely botanical sense. (See F. Koernicke, 

 Handbuch tier Getn-idc, 1885.) In the group of cereals "varieties" usually are collective 

 notions, and some of them include many independent morphological and physiological 

 forms — "races" — the smallest systematic units. 



- Parenthetically we must remark that the definition of degree of susceptibility to a 

 certain disease is not quite simple. In fact, the exactitude of many old works in this 

 respect is so small that in our days we are obliged to obtain these data anew. More 

 details about the definition of degree of immunity are given in our paper (16), Chapter i. 



