3T0 



With the action of sudden cold, lasting for several hours, Haberlandt' 

 found that a noticeable change occurred at a temperature of minus 4 to 6 

 degrees C. and only at minus 12 to 15 degrees C. does the destruction of the 

 chlorophyll grains become complete (with the exception of those in ever- 

 green plants). With the formation of vacuoles there was produced a dis- 

 tortion of the form of the chloroplasts which were either passing over into 

 the position along the side walls (apostrophe) or were rolled up in lumps. 

 Of these the ones inclosing ttarch grains were destroyed more quickly than 

 those without starch. In the leaves of Vicia odorata no difference could be 

 perceived in the destruction of the chlorophyll, dependant upon the age of 

 the leaf. 



We will touch upon this subject again under autumn coloring. A 

 yellow leaved condition in spring is found often in pears growing in nurse- 

 ries, as the after effect of frost disturbances. 



The grape is very susceptible to icteris. Different factors have been 

 recognized here as the cause. In the cases observed by Mach and Kiirmann- 

 in the Tyrolean vineyards, the analyses of green and icteric vines, growing 

 close together, showed: 



Water Content of the yellow leaves 77-97 per cent. 



Water Content of the green leaves 73-17 P<-'r cent. 



Based on dry weight, the green leaves possessed a higher percentage of 

 organic substances and of nitrogen, but considerably less ash. The ash of 

 the yellow leaves contained six times as much of the elements insoluble in 

 hydrochloric acid as did that of the green leaves. On the other hand, there 

 was less potassium in the former. Watering with liquid stable manure 

 acted beneficially. A similar case is described by E. Schultz^. The leaves 

 and woody portion of the diseased vines contained only half as much potas- 

 sium as those of the healthy plants, which were found, however, to be 

 poorer in calcium and magnesium. Besides this icterus due to a lack of 

 potassium, a jaundice of the grape, resulting from an excess of calcium, has 

 been determined by numerous observations. It seems to me that the amount 

 of calcium in itself is not the injurious factor, but chiefly the lack of potas- 

 sium, since calcium soils, as a rule, are poor in potassium. We will return 

 to this case in the section on the excess of calcium. 



Nitrogen starvation is also a frequent cause. This, differing from the 

 phenomena due to a lack of other nutritive substances, does not manifest 

 itself in the death of the plant in an early stage but only retards the growth 

 and reduces all the organs to a minimum. 



The oft repeated experiments with the cultivation of non-leguminous 

 plants in nutrient mixtures without the addition of nitrogen have shown 

 that under otherwise favorable conditions, with certain races, a new min- 



1 Haberlandt. tlber den Einfluss des Frostes auf die Chlorophyllkorner. Osterr. 

 Bot. Zeit. Cit. Jahresbericht, 1876, p. 718. 



2 Biedermann's Centralbl. 1877, p. 58. 



3 Zeitschr. d. landwirtsch. Centralver. fiir das Grossherzogtum Hessen. cit. 

 Centralbl. f. Agrikulturchem. 1872, p. 99. 



