IQ 2oJ WALSTER— BARLEY 99 



soon outstripped the high temperature plants, finally reaching twice 

 the size. Figures of Appel and Gassner's plants show that there 

 was an excessive leaf production and little stem production at the 

 higher temperature. These investigations suggested that the 

 light color of the leaves was due to nitrogen hunger, but they were 

 unable to get any beneficial results from nitrogen fertilization. 

 The addition of iron salts also had no favorable effect. 



Gassner (3) has made extensive observations and experimental 

 studies upon the growth and development of cereals in subtropical 

 climates, the experiments being carried out in the phytopathological 

 experimental fields of the University of Montevideo, Uruguay. 

 In considering the choice of varieties of summer cereals suitable 

 for cultivation in Uruguay, he emphasizes the importance of temper- 

 ature in the early stages of development, and suggests that decreased 

 yields are often due to the lack of the necessary cold requirements 

 (Kalteanspruche) in the early stages of growth. Gassner quotes 

 Hellriegel (6) on the temperature relations of small 4-rowed 

 barley. Hellriegel maintained that in the first half of the 

 vegetative period of the barley, the period of leaf and culm forma- 

 tion, an average daily temperature of about 15 C. is the best, 

 whereas in the second half of the vegetative period, the period of 

 head development and grain formation, a temperature of 17-18 C. 

 is the most favorable. Hellriegel therefore insists upon two 

 different temperature optima in development of barley, the line of 

 demarcation between the two optima being placed at the time of 

 shooting. 



Gassner summarizes his views as follows (translated from the 

 original article) : 



We can therefore say that for winter cereals, as well as for summer cereals, 

 the yield- of a given variety of a cereal in a given climate is among other things 

 dependent upon the influence of the climatic factors in the first stage of develop- 

 ment in such a way that varieties of high "cold requirements" in their youth 

 require a colder climate than varieties with lower "cold requirements," and 

 that incomplete fulfillment of these requirements causes bad development and 

 depression of the yield. 



Gassner states that the death and yellowing of the leaves of 

 young plants previously described by Appel and Gassner rarely 



