PAMMEL ON THE SEED-COATS OF EUPHORBIA. 553 



•{Cydonia) vulgaris, Linum, and other cases mentioned by him, 

 agree in the chemical reactions with the substance of the cell-wall. 



Cramer was of the opinion that the mucilage in Linum is a 

 transformed product of the starch-grains contained in the epider- 

 mal cells. Hofmeister considered that this substance was con- 

 tained in the outer membrane of the epidermal cells, and in its 

 chemical behavior resembled the mucilage of the quince. The 

 mucilage of flax is insoluble in cupra ammonium, but the Plan- 

 tago mucilage is readily soluble in that substance. Uloth^'' ex- 

 tracted the mucilage of 150 seeds of Plantago^ and only obtained 

 0,045 per cent, of mucilage. The extracted mucilage again swells 

 in the presence of water. Alcohol precipitates it, and micro- 

 chemical tests show that the substance has not been changed by 

 separation. Iodine and chloriodide of zinc, or iodine and sul- 

 phuric acid, do not cause any change. 



Abraham^ ^ says in regard to the reaction of the mucilaginous 

 cells in C r7icife7-ce : •' The substance is insoluble in water, solu- 

 ble in potash ; and iodine and sulphuric acid cause the usual 

 reaction." 



The Euphorbia mucilage seems to be related to that of Ru- 

 ellia^ Liuuin^ Ocimum^ Salvia, &c. 



I have taken up only the species of Euphorbia of the new edi- 

 tion of Gray's Manual.*^ Only six of the twenty-seven sections 

 established by Boissier^° occur within the limits of the Manual, 

 while only eight occur in the United States, according to Dr. 

 Engelmann.^ ' 



Anisophyllu7)i is represented by nine species in the new Man- 

 ual. The seeds, with the exception of E. Preslii, are ash-col- 

 ored, while those of the latter are blackish. The different sections 

 are readily separated by seed characters. These are shown on 

 plate xii., figures 1-9. The white outer part which covers the 

 seeds of some of the species is smooth and shining. An examina- 

 tion of ripe seeds will show that in many cases, as in E. polygo- 

 nifolia, this part has been removed so that some appear brown. 



47. L. c. 4S. L. c. 



49. Watson & Coulter: Gray's Maaual of the Botany of the Northern United States , 

 Revised edition, 1S90, p. 452. 



50. DiiCandoUe : Prodromus, vol. xv. 11, p. 8. 



51. On the Kenus Euphorbia: Amer. Jour, of Sci., Scr. 2, vol. xxxiv, ; Engelmann 

 Reprint, p. 441-445. 



