556 



WEED FLORA OF IOWA 



Fie. 424. Microscopic structure of the seed of common Geranium (Geranium 



caro linianum ) . 

 ep= epidermis. p=parenchyma, malpighian cells below. ll=llght line of mal- 

 pighlan cells. pal=palisade cells. it=lnner testa. n=nucellus. en=en- 

 dosperm. 



(Drawing by L. H. Pammel and Charlotte M. King.) 



BUPHORBICEAE,* SPURGE FAMILY. 



Flowering Spurge {Euphorbia corollata L.). 



The outer layer of the seed coat is mucilaginous; the walls of 

 the cells are thickened and colorless; showing stratification upon 

 addition of water; the cell contents are dark in color. The granu- 

 lar layer beneath the mucilaginous cells is well developed ; the con- 

 tents give a blue reaction to iodine. Underneath the granular 

 layer is a row of slightly elongated thin-walled parenchyma cells; 

 beneath these are the long palisade-like cells, in which are pores 

 of less prominence than in E. marginata and others. Next lie two 

 compressed layers of thin-walled parenchyma cells. 



Spotted Spurge (Euphorbia preslii Guss.). 



The outer layer of cells are darkened; these cells are not 

 mucilaginous. The palisade-like cells are present, as in all the 

 species. 



•The descriptions here given are from a paper by L. H. Pammel, Trans. 

 Acad. Sci. St. Louis. 5:543. The literature will be found in this paper. 



