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leaves in which the cholorophyll has been destroyed. The red coloring mat- 

 ter is soluble in water and glycerin, insoluble in alcohol and turpentine, 

 turning blue with potassium and ammonia and again red with acids. It is in 

 combination with the cell sap, partly in the epidermis, partly in the assimila- 

 tary tissue. In oats, the development of the reddened plants and their grain 

 production was proved to be less than that of green ones. We have just made 

 a study of the reddening of grains^ and, in agreement with Klebahn, have 

 come to the conclusion that in this redness only phenomena of a premature 

 ripening are to be seen, together with a lack of moisture and great intensity 

 of light. In our treatise will be found also anatomical details as to the 

 blasting and the appearance of the so-called "drought spots." A yellow 

 coloration of the walls of the bast fibres is worth noticing, which increases 

 to a yellow brown, as is also the hardening of the cell contents in various 

 groups of the assimilatory tissues. 



The death of leaves, due to sudden heat periods, should be distinguished 

 from a normal death. The leaf does not shrivel up as completely as the nor- 

 mally ripened one, — i. e., a leaf, the contents of which are nearly exhausted — 

 or it can do so only in places. In the normally ripened leaf, only the entirely 

 impoverished cells of the leaf tissue, which therefore collapse to a waved 

 folded layer, are found between the epidermis of the upper and of the lower 

 sides, while in the former leaf just the remaining, more abundant contents 

 stiffen the walls by drying, thereby more or less preventing the collapse. 



I also found the same discoloration phenomena in wild grasses (Arrhen- 

 atherum) and expressed a warning against deceptions from anatomical in- 

 vestigation. Especially angular or spherical masses appeared in the contents 

 which reacted with iodine like starch and thereby could give the appearance 

 of a still existing, greater assimilatory activity. The other reactions prove, 

 however, that "residue bodies" of the chlorophyll decomposition are here in- 

 volved which belong to the carotin group. They could be compared with 

 adipocere. 



"Reds" of Hops. 



The disease, called by practical growers "summer rust/' "Fox" or "red 

 tan," consists in a spotting of the leaves, which advances from their bases. 

 The spots attack the peripheral parts as well as the tissue groups lying 

 between the different veins. By a partial destruction of the chlorophyll, the 

 diseased places at first appear yellowish, then reddish and finally dry and 

 browned. In the meantime the leaf continues longer in a wilted condition, 

 finally, it shrivels and drops off, while the upper, younger parts of the vine 

 are still fresh, green and developing. The new structures produced during 

 this time are smaller in comparison with those of other plants which are un- 

 affected and have not lost the lower leaves. If the disease remains restricted 

 to the lower parts of the vine, the injury is not important; but, if it attacks 



1 Sorauer, P., Beitrag zur anatomischen Analyse rauchbeschadigter Pflanzen. 

 Landw. Jahrb. 1904, p. 596, Plates XV to XVIII. 



