i9i 7] W EN IGER— EUPHORBIA 269 



of the other cells of the row adheres to the developing sac for some 



time before it disintegrates. 



According to Modilewski, the embryo 

 salicifolia, E. globosa, E. meloformis, E. Cyp 



LathyruSy 



heteroph 



helioscopia, E. Gerardiana, E. Ip 



Dessiatoff (4) describes the for- 



mation of 16 nuclei in E. virgata, in a manner similar to that described 

 by Modilewski for £. procera (n). In a still later study, Modi- 

 lewski (13) finds 16 nuclei in the embryo sac of E. palustris. 

 The development proceeds exactly as in E. procera. On the other 

 hand, the embryo sacs of E. virgata and E. lucida develop in the 

 ordinary way. Modilewski, whose material for the study of 

 £. virgata was collected from various localities, disagrees with 

 Dessiatoff's notion of the structure of the embryo sac in this 

 species (4). He thinks that the nuclei in Dessiatoff's i 

 of the embryo sac resemble endosperm nuclei more than they do 

 those of ordinary embryo sacs. He finds, also, that at the 2- and 

 4-nucleate stages the megaspore enlarges so rapidly that its wall 

 becomes indistinct, and that the cells of the nucellus. which have 

 been pushed aside in the growth of the spore, might easily be 

 taken for nuclei of the developing gametophyte. Dessiatoff, 

 according to Modilewski, mistook either endosperm or nucellar 

 nuclei for nuclei of the mature embryo sac. If this is not the 

 explanation of his results, Modilewski thinks Dessiatoff was 

 mistaken in the determination of the species studied. Mo BIOS do) 

 has recently figured the relation of the integuments and obturator 

 to the nucellus in E. macrorrhiza. 



E. procera and E. palustris, on the present evidence, seem to be 

 the only species of Euphorbia studied which deviate from the usual 

 history of the embryo sac. In these species, Modilewski found 

 that since the endosperm nuclei are very large and usually contain 

 2 or 3 nucleoles, there is no danger of their being confused with the 

 nuclei of the mature embryo sac. 



Material and methods 



Flowers and seeds of Euphorbia Preslii were collected in differ- 

 ent stages of development during July and August 191 5, along 



