TISSUES AND SIMPLE ORGANS. 



89 



our immediate attention. Apparently radially comj)ressed, narrow- 

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

 summer- wood. On the other hand wide-Iumened, 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: b, bast; I, leptonie; c. cambium; If, libri- 

 fonn tissue ; Ht, mestonie; ^, 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 yearly rings, is 



