lasting all day, but older ones were affected and finally died. I found 

 similar conditions in plane trees in which the age of the tree made itself felt 

 in the same way. In street trees, young specimens had been planted be- 

 tween the older trees. Although they did not stand under the protection of 

 the older trees, they still retained their considerably stronger foliage when 

 most of that of the older trees lay on the ground. 



Behavior of Bef.t and Cabbage Plants in Frost. 



In storing sugar beets the loss of sugar, which occurs in the heaps 

 because of the respiration of the beet body, can be decreased only by the 

 lowest possible temperature\ In sugar beets which have been frozen, a 

 raising of the sugar content was actually found when the water was frozen 

 out. This has been reckoned by Ninger to be 0.39 per cent'-. 



The new formation of saccharose which takes place during the process 

 of freezing is no greater than the amount destroyed. Also the amount of 

 nitrogenous substances and the proportion of proteins to non-proteins re- 

 mains unchanged. So soon, however, as thawing begins, the latter appear 

 to be increased at the expense of the former. The elements of the raw^ 

 fibers (cellulose and related substances) become more soluble in acids and 

 alkalis and in part also more soluble in water because of the freezing^. In 

 this an increase of non-sugar substances is produced in the sap. I observed 

 in frozen beets partial swellings of the membranes which might be ex- 

 plained as a visible expression of the chemical changes in the cellulose. 

 Strohmer and Stift found a striking increase in the acid content. 



The large sugar content, produced by the loss of water, and the conse- 

 quently more concentrated cell sap will, however, retard the actual freezing 

 of the beet body. Besides this, in the storage piles, the outer, frozen tubers 

 will protect the inner ones from freezing. Miiller-Thurgau has referred to 

 this especially and Mez* has explained it by the fact that the conversion 

 of the cell sap into a solid aggregate condition preserves the energy still 

 present in the cell from too rapid dispersal. The conduction of warmth 

 takes place much more slowly in ice than in water, where the warmth is 

 distributed by radiation. 



The statements of market gardeners that brown cabbage (Brassica 

 oleracea acephala) obtains its desired sweetness only after frost, may find 

 adequate explanation in the accumulation of sugar due to the low tempera- 

 ture. According to the analyses made by Marker and Pagel^, an amount 

 of sap equal to 68.66 per cent, of the remnants of the plant may be pressed 



1 Heintz, Atmung' der Riibenwiirzeln. Zeitschrift d. Ver. f. d. Riibenzuckei'in- 

 dustrie d. deutsch. Reiches 1873. v. XXIII; cit. Bot. Jahresb., I, p. 358. 



2 Bot. Jahresber. 1880, p. 665. 



3 Strohmer, F. und Stift, A., tjber den Einfluss des Gefrierens auf die Zusam- 

 men-setzung- der ZuckerriJbenwurzel. Osterr-Ung. Z. f. Zuckerindustrie und Land- 

 wirtsch. 1904. Part 6. 



4 Mez, Carl, Neue I^'ntersuchungen iiber das Erfrieren eisbestandiger Pflanzen. 

 Send. Flora od. Allgem. Bot. Zeit. 1905, p. 109. 



5 Marker und Pagel, tJber den Einfluss des Frostes auf Kohlpflanzen. Bieder- 

 mann's Centralbl. 1877, v. XI, p. 263-66. 



