Grossenbacher Radial Growth in Trees. 47 



tion and duration of growth, in the early and late season, over 

 the different parts of a tree. That is, if in any particular re- 

 gion of a trunk radial growth starts very early in spring and 

 continues rapidly to the end of the spring-growth period a con- 

 siderable layer of spring wood will occur in that region; while 

 if spring growth starts late, proceeds slowly and stops rather 

 early the thickness of spring wood would be slight. If the dis- 

 tribution of summer growth is such as to add but little to a re- 

 gion where spring growth had been heavy and much where 

 spring growth had been slight, the rings resulting in the two 

 regions would have a very different appearance. To continue 

 the illustration further, if for some reason radial growth failed 

 to occur in certain parts of a tree-trunk until after the produc- 

 tion of summer wood had begun such parts would show only 

 small-lumened, thick-walled cells in the ring ; while had the sum- 

 mer growth been eliminated in regions where spring growth oc- 

 curred the resulting ring would consist of spring wood only. 

 From the papers cited above on the distribution of radial growth 

 it is evident that all the cases illustrated here do actually occur 

 even in the extreme forms used in the last illustration. It is ap- 

 parent, therefore, that in some environments and especially on 

 certain parts of trees the distribution of radial growth may have 

 a marked influence not only on the type of the resulting ring 

 but even on the nature of the wood in such portions of stems. 

 This evident relation between the seasonal distribution of radial 

 growth on a tree to the type of wood ring to be produced has 

 reseived practically no attention, although in von Mohl 's 93 paper 

 on the anatomy of roots it is noted that rings with only the spring 

 type of wood seem to result owing to the entire omission of the 

 summer growth; while Sanio 94 suggested a similar idea regard- 

 ing the absence of spring growth in parts of some rings of a 

 dwarfed Fraxinus grown in a swamp. Lutz 95 also noted the ab- 

 sence of summer wood in a pine, from which the buds had been 

 removed in March, the little growth that occurred was spring 

 wood. When the wood of roots or stems grown in certain en- 

 vironments consist largely of so-called spring wood, elaborate 

 explanations are usually manufactured to show that the high 



"1. c. 

 4 1. c. 



* 1. c. 



