It is well known that, in sDnic years, such premature (le\ el(i|iment of 

 inflorescences occurs often in other plants, which form fleshy, storage 

 organs (celery, carrots, radishes). Jt is very i)rohable that not only frost 

 action hut also other processes (jf arrestment are effective here. 



I'^kosTV Taste in GRArES. 



The processes which occur in the turning sweet of potatoes take place 

 also in woody plants. In this connection, Pfefifer' mentions Fischer's inves- 

 tigations'- on the Huctualions hetween the starch and sugar in the so-called 

 starch trees, such as the linden and birch'. W hen branches are taken in 

 winter from out of doors into a warm room, starch is formed in the bark 

 parenchyma, within a few hours, and, in the cold, can again pass over into 

 sugar. A similar formation of sugar, connected with tlie decrease of 

 organic acids, is found to occur in grapes after the action of frost, 



I'^en when the main stem of immature clusters had been attacked by 

 frost but was still green and the berries clear, a considerable decrease of acid 

 and increase of the sugar content was founds An investigation on Riesling 

 grapes of the decrease of acids in a ])lant which had been exposed from 

 October 19 to November 9 to a temperature as low as 5 degrees C. proved 

 an acid reduction of 4 per cent. Half ripe clusters, greatly injured by frost 

 when cut off, showed from October 1 to 11, an acid loss of 4.5 per cent. 



The frosty taste, however, does not seem to be due alone to the increase 

 of sugar and decrease of acid, but material compounds may perhaps diffuse 

 from the stems of the grapes which the protoplasm of cells would not have 

 let pass through, if there had been no frost action. Through these changes, 

 the susceptibility of the grapes to the fungus of white rot may be increased, 

 since Viala and I'acottet"' have shown that this fungus is able to infest only 

 the berries which ha\e a high sugar and a smaller acid content. The be- 

 havior of black rot is exactly the reverse. 



Chances in the Blossom Organs. 



In the action of frost, the permanent processes are sometimes chemical, 

 sometimes mechanical. In the former it is difficult to decide in how far they 

 are initiated by the freezing, or if they begin only with thawing. Thus for 

 example, (i()i)pert''' has obserxed in the blossoms of Phajus and Calanthe 

 that they turned blue when frozen. Tliis change in color is explained by 

 the fact that, through the action of the frost, the indicans, which is abun- 

 dant in the normally colorless cells, especially around the vascular bundles, 



1 I'hysiologie, 2d edition, I, p. 514. 



-• .Jahib. f. d. wiss. Hot. 1891, v. XXII. 



■'• t)ber die Periodizitiit der Starkezii- und aJm.ihme in den Biinmen. Compare 

 Mer, E. in Bot. Jahresb. 1891, I, p. 46. 



* Hiedeimanns Centralbl. 1879, I, p. 23.S. 



•"' Viala, P. et Pacottet, Sur la culture du black-rot . Compt. rend. 1904, 

 CXXXVIII, p. 306. 



•i tUier Einwirkung des Frostes auf die Gewachse., Sitzungsber. d. Schles. 

 Ges. f. vaterl. Kultur 1S74, cit. Bot. Zeit. IST.'i, p. 609. 



