PAMMEL ON THE SEED-COATS OF EUPHORBIA. 555 



tospcrma is due to the outer row of cells, which are more or less 

 arranged like papillre, as is shown in figure i, plate xiii. The cells 

 in both cases are plainly stratified before the addition of water. 

 On the addition of water these cells immediately elongate as 

 shown in figure 13a. Stratification is well preserved in sections 

 mounted in glycerine jelly. Microchemical tests were not made. 



Underlying the outer row of cells the granular layer occurs. 

 On the addition of iodine the granules color blue, showing the 

 presence of starch. The palisade-like layer is not so well devel- 

 oped in these species. It is followed by several layers of thin- 

 walled elongated cells. Above the palisade-like layer a row 

 of thin-walled cells occurs. 



In £. mac 111 at a the walls of the outer cells are of darker color, 

 and the granular layer is not so pronounced. The palisade-like 

 cells resemble those of the other species. E. hitinistrata is much 

 like E. niaculata. In E. Preslii the outer layer of cells is not 

 colorless as in the other species. 



E. hexagona^ which is the only representative of Zygophxl- 

 lidium in the region covered by the Manual, has tuberculate 

 seeds. In some cases the seeds are covered with an ashy 

 substance ; in others, they are of a darker color. A section 

 through a seed shows that the ridges are produced by large cells 

 which project out as shown in plate xiii., figure 10, more magni- 

 fied at fig. \o B. Sometimes only a single cell occupies this ridge, 

 in other places two or more may be found. In the depressed 

 portions of the seed the mucilaginous cells are less developed. 

 (See fig. 10 C.) The cell-walls in all these cases are plainly stra- 

 tified before the addition of water ; on the addition of water, the 

 cells immediately elongate. (See fig. 10 (5a'.) In the depressed 

 portions the cell-cavity is small, and contains a brown substance. 

 On addition of iodine the colorless cell-walls do not change, but 

 when sulphuric acid was also added they became blue. The 

 granular layer is well developed underneath the mucilao-inous 

 cells. On addition of iodine the granules color blue. The pali- 

 sade-layer is made up of three parts, a lower and an upper, 

 separated by an intermediate portion. In these the cells are 

 rounded and somewhat elongated. The palisade-like cells are very 

 thick, and, unless a good section is obtained, the structure is not 

 readily made out. The pores of these cells are well developed, as 



