DISTINCTIONS IN CULTIVATED BARLEYS. 27 



forms and has been the cause of much of the progress that has been 

 made in the isolation of biotypes. 



Neergaard's work was based upon the careful study of the spike. 

 He discovered that two previously unobserved variants were de- 

 pendable morphological distinctions. These were the nature of the 

 covering of the basal bristle and the toothing of the inner pair of 

 dorsal nerves. The basal bristle, which is the continuation of the 

 rachilla of the spikelet, is clasped within the folds of the glumes 

 and is carried with the kernel when it is removed from the spike in 

 the process of thrashing. The bristle is covered in some cases with 

 long, stiff hairs; in others, with short, curly ones. The inner pair 

 of nerves upon the dorsal surface of the grain are in some cases pro- 

 vided with numerous, small, translucent teeth; in others they are 

 smooth. 



The use of these two new characters gave four separations in any 

 group, i. e., long-haired bristle and nerves without teeth, long-haired 

 bristle and nerves with teeth, short-haired bristle and nerves without 

 teeth, and short-haired bristle and nerves with teeth. When these 

 separations were applied to the larger groups, Hordeum sativum 

 erectum, Hordeum sativum nutans, and Hordeum sativum vulgare 

 {tetrastichum) , 12 smaller groups resulted. 



Although this new grouping was only a small part of the Svalof 

 observations on barley, it soon became known as the Svalof system, 

 due no doubt to its novelty. As a new departure it has been subject 

 to much more controversy than have most of the older and univer- 

 sally accepted taxonomic features. Several breeders, among whom 

 Broili (10) is the most notable, have attacked the system and de- 

 clared that, though the characters might be trustworthy at Svalof, 

 when the plants were grown under other conditions they did not re- 

 main constant. Tschermak (13, p. 286) , Blaringhem (7) , and others, 

 have supported the investigators at Svalof in the matter of the basal 

 bristle, but have not committed themselves so completely with ref- 

 erence to the toothing of the nerves. Since the point of contention 

 is the effect of soil and climate, observations in this country are of 

 many times the natural value of those in Europe. The variation be- 

 tween California and Minnesota or Idaho and Virginia represents a 

 range that is impossible to a European breeder. 



Observations have been made upon some hundreds of selections 

 representing all botanical groups. Very little variation was found 

 in the nature of the rachilla. All observations tend to credit this 

 character with as much stability as is usually found in taxonomic 

 work. As would naturally be expected, the toothing of the dorsal 

 nerves has been found to be more. variable and more influenced by 

 climate. The rachilla is the axis of the spikelet, a definite and vital 

 portion of the fruiting body. The 'teeth on the dorsal nerves are of 



