8 Wisconsin Academy of Sciences, Arts, and Letters. 



cases root growth may precede the growth of aerial parts of trees 

 in spring. 



Schwarz 19 found that radial growth may start in spring in 

 various parts of trees depending on the environment. In case of 

 a much shaded or overtopped tree it was found that radial 

 growth had begun at the base, while half way up the trunk the 

 cambium was still .dormant. In another instance 43% of the 

 ring had formed at the base of a tree by July 27, while 5.5 m. up 

 the trunk no growth had yet occurred. These irregularities are 

 held not to be attributable to differences in temperature occurring 

 at the different regions. Mechanical stimuli to be discussed 

 later are held to be the instigators and distributors of radial 

 growth. 



THE RELATION OP FOOD DISTRIBUTION AND THE PRESENCE OP 



ELONGATING STRUCTURES TO THE OCCURRENCE OP RADIAL 



GROWTH. 



It is of interest to know definitely what relation exists between 

 the occurrence of radial growth and elongation growth or 

 whether both are simply dependent upon the presence of certain 

 unknown amounts of elaborated and inorganic foods in connec- 

 tion with the en2ymes that may be involved in food transforma- 

 tions and growth. The experiments of Jost 20 indicate that a cas- 

 ual relation exists between radial growth and some phases of elon- 

 gation growth or the presence of unfolding buds, since on the re- 

 moval of the buds from seedling beans radial growth practically 

 ceased although elongation might continue. Starch was present in 

 abundance and increased after the operation yet cambial activ- 

 ity remained in abeyance. All the elongation buds were re- 

 moved from several years growth of branches of Pinus Laricio 

 on March 8 while the dwarf branches and their leaves were al- 

 lowed to stay. The dwarf branches which were nearly terminal 

 then developed elongation buds. By the end of May but few 

 tracheids had developed in the decapitated branches while in 

 normal branches a new layer of about twelve tracheids was pres- 

 ent, and they had become lignified. A month later the mutilated 



19 Schwarz, F. Physiologische Untersuchungen fiber Dickenwachstum 

 trad Holzqualitat von Pinus silvestris. Berlin. 1899. pp. 371. 



*> Jost L Ueber Dickenwachstum und Jahresringbildung. Bot. 

 Zeit. 49:485-95; 501-10; 525-31; 541-47; 557-63; 573-79; 589-96; 

 605-11; 625-30. 1891. 



