TISSUES AND SIMPLE ORGANS. 



89 



our immediate attention. Apparently radially compressed, narrow- 

 lumened, thick-walled elements mark off the autumn-wood or 

 summer- wood. On the other hand wide-lumened, thin- walled, 

 radially elongated, or, at least, not radially shortened, cell-forms 





FIG. 54. Section of a ring of the previous year's growth. Cystisus Laburnum. 



m, Medullary rays; p, secondary bark-parenchyma: ft, bast; Z, leptome; c, cambium; If, libri- 

 form tissue; m, mestome; g, year's limit. (After Haberlandt.) 



belong to the spring- wood. Among angiospermous trees this con- 

 trast is strongly marked by the minuteness or absence of vessels in 

 the autumn -wood as compared with the large size and great numbers 

 of the same in the spring- wood. This difference, which is usually 



visible to the naked eye and which marks off the 



rings, 



is 



