Grossenbacher — Radial Growth, in Trees. 7 



species he says that root growth had also "started more or less 

 in advance of the buds : " Picea excelsa, P. alba, P. pungens, 

 Pseudotsuga Douglasii, Abies concolor, Thuja occidentalis, Pinus 

 sylvestris, Tsuga canadensis, Tamarix amurensis, Acer sacchari- 

 num, Pyrus Malus, P. Communis, Prunus cerasus, P. vvrginiana, 

 Betula alba, Morus alba, 'Gornus stolmifer, Eleagnus hortensis, 

 Ribes nigrum and R. oxyacanthoides. "When these observations 

 are compared with those of von Mohl 15 who found that, though 

 radial growth in conifers has practically ceased by winter and 

 that in deciduous trees it usually has not, it seems likely that Goff 

 overlooked the possibility that portions he held to be new spring 

 growth may have been very late growth of the preceding fall. 

 Hartig 16 found that the roots of various forest and fruit trees 

 had ceased radial growth in January, as judged by the thickness 

 of the new ring and by the presence of starch in all of the ray 

 cells of the cambial region. Kussow 17 made similar observations 

 in regard to both forest and fruit trees. Hartig notes an excep- 

 tion in the case of a species of willow where radial growth of the 

 roots had not been completed as shown by the thinness of the 

 ring as well as by the absence of starch in the ray cells of the 

 cambial region. Resa 18 also made some observations which sup- 

 port Goff in some cases at least. He found that the roots of 

 Picea and Fagus ceased growth in November and recommenced 

 in February and March, while in case of Aesculus Mippocastan- 

 um and Tilia root growth ceased in October and recommenced 

 in December or later. In Alnus glutinosa root growth began in 

 October and continued practically through the winter except 

 when the ground was frozen. Root growth began in late May in 

 Acer campestre and in June in Quercus Robur. It is not usually 

 considered that such enormous variations occur in the root 

 growth of our trees and shrubs and for want of more detailed 

 information it seems necessary to admit that at least in some 



16 von Mohl, H. Einige anatomisehe und physiologische Bemerkun- 

 gen iiber das Holz der Baumwurzeln. Bot. Zeit. 20:225-30; 233-39; 

 268-78; 281-87; 289-95; 313-19; 321-27. 1862. 



18 Hartig, Th. Ueber die Zeit des Zuwachses der Baume. Bot. 

 Zeit. 21:288-89. 1863. 



" Russow, B. Tiber den Inhalt der parenchymentischen Elemente der 

 Rinde vor und wahrend des Knospenaustriebes und Beginns der Cam- 

 biumthatigkeit in Stamm und Wurzel der einheimischen Lignosen. 

 Stizungsber. Naturforscher-Ges. 6:386-88. 1884. 



18 Resa, F. Ueber die Periode der Wurzelbildung. Inaug. Dissert 

 Bonn. 1877. pp. 37. 



