Variation in the Food Reserves of Trees. 235 



species, Sablon believed, deposit their reserve cellulose within 

 rather than upon the wall of permanent cellulose. 



In 1895, Schellenberg^ strengthened the position of Sablon re- 

 garding the annual formation of reserve cellulose in trees. In 

 the xylem parenchyma of Aescnlus hippocastanum, Betiila ver- 

 rucosa, the Beech Oak, Ash and Alder, though there was an un- 

 lignified inner lamella, this was never dissolved, because the cells 

 died at the end of the season of their formation. But in Vitis 

 vinifera and Robinia pseud-acacia, these xylem parenchyma cells 

 do not die so early, and their inner lamellae are partially dissolved 

 the following spring. The primary cortex of young twigs may 

 be used for deposit of reserve cellulose, as in the case of the 

 Birch, Alder, Hazel and Horsechestnut, and most probably in 

 Salix capraea, Quercus penduculata, Populus and Fagus silvatica 



The parenchyma of the phloem was seen to dissolve partially 

 its cellulose in Alnus, Aescnlus hippocastanum, Betula, Pinus 

 montana, Larix europaea, and Picea excelsa. 



The deposit of the reserve cellulose takes place from August 

 till October, or even to the end of November in some species, the 

 walls being seen to thicken. In the spring, the solution of the 

 cellulose is determined by an actual thinning of wall in some 

 cases, and by a partial solution without much thinning in others, 

 the loss of density in the wall being shown by polarizing appa- 

 ratus. 



Niklewski's^ study concerned chiefly the fat content of Tilia, 

 Betula, Prunus and Syringa. Unlike Vandevelde,^ who found 

 fat not changed in amount when the starch of autumn is dis- 

 solved, Niklewski found fat increasing from summer into Janu- 

 ary, and, after that, a decrease till summer. But Vandevelde and 

 Niklewski agree that the amount of fat present is not directly 

 related to the transformations of starch. Starch can be changed 

 to sugar and sugar to starch by varying the temperature; but 

 the formation of fat is a seasonal function, largely independent 

 of temperature. 



^Ueber Hemicellulosen als Reservestoffe bei unseren Walbaumen. Ber. 

 d. d. bot. Gesellsch. XXIII, 1905, 36. 



'Untersuchungen iiber die Umwandlung einiger stickstofffreier Re- 

 servestoffe wjihrend der Winterperiode der Baume. Beih. Bot. Centrblt. 

 XIX, 1906, 68. 



^Bijdrage tot de scheikundige physiologie van den stam der Boomen. 

 Ghent, 1905. (This paper w^as inaccessible to the present authors.) 



