306 



SCIENCE. 



[N. S. Vol. XI. No. 269. 



minimum and the toxic action is due solely 

 to unionized molecules. 



Further notes on the Embryology of the Ruhi- 

 acece : Peofessor F. E. Lloyd, Teachers 

 College. (By invitation.) 

 The Rubiacete reported upon up till now 

 include the Stellatce. The present paper deals 

 with Diodia virginiana, D. teres, Richardsonia 

 pilosa and Cephcdanthus occidentalis. All are 

 similar morphologically as to the topography 

 of the ovule. They vary, however, in the 

 relative rapidity of development of the basal 

 partition and of the nucelli. Cephalanthus 

 possesses the most rapidly developing basal 

 partition with the result that the ovule is 

 rotated so that the funicle is inserted in the 

 top of the ovary and the embryo sac is in- 

 verted. All possess an outgrowth of the 

 funicle, resembling a second integument, 

 which in Richardsonia and Diodia becomes 

 loaded with raphides and is believed to 

 have a nutritive role. The ' spongj' ' funic- 

 ular appendage in Cephalanthus is shown 

 to be the homolog of that in Diodia and 

 Richardsonia, but the nutritive function is 

 here less probable. The funicle in Diodia 

 and Richardsonia is surrounded bj' a collar 

 of peculiar epithelial cells which in Richard- 

 sonia are the path of the pollen tubes ; the 

 latter never travel freely in the ovarian 

 cavity. The archesporium consists of but 

 one cell which gives rise to four megas- 

 pores. One of these is the embro-sac 

 mother cell. The embryo-sac is of the 

 elongated type with the usual number 

 of cells. One of the antipodal cells is 

 rather long in Diodia, but the three are of 

 equal size in Richardsonia and Cephalanthus. 

 Diodia virginiana, however, has four antip- 

 odal cells from the division of the long 

 cell after the small ones are cut off. The 

 embryo possesses a short cylindrical sus- 

 pensor from which the haustoria character- 

 istic of the StellatcB are absent. There is, 

 however, evidence of a nutritive function. 



The embryo develops at first very slowly, 

 in contrast with its rapid early development 

 in the Stellatce, a fact which is correlated 

 with the absence of haustoria. The endo- 

 sperm at first is parietal. 



The stimuli that cause the so-called 'peg' or 

 ' heel ' on Cucurhita seedlings : Dr. J. B. 

 Pollock, University of Michigan. 

 No abstract of this paper is available. 



On the prothallus of Taxodiimi distichxim Eich- 



ard: Mr. \V. C. Coker, Johns Hopkins 



University. (By invitation.) 



The archesporium consists of a group of 

 cells near the base of the nucellus. One of 

 its central cells enlarges at the expense of 

 those' around it and becomes the embryo- 

 sac. The archegonia arise at the upper 

 end in a group and soon come to lie in a 

 depression, which is at first covered over 

 by the wall of the embryo-sac. There are 

 four neck cells, and a ventral canal cell is 

 cut off. Soon after the formation of its 

 cell-walls the endosperm cells become mul- 

 tinucleate by amitotic division. 



The pollen sprouts soon after pollination 

 (which in Baltimore takes place about the 

 middle of March) and reaches the embryo- 

 sac before a solid endosperm has been 

 formed. The end in contact with the sac 

 now contains three nuclei, not greatly differ- 

 ing in size, one of which is the body cell 

 nucleus. This increases in size, surrounds 

 itself with a dense mass of cytoplasm, and 

 just before fertilization divides into two 

 male pro-nuclei each with its mass of cyto- 

 plasm. Several pollen tubes may push 

 their much enlarged ends into the depres- 

 sion in the embryo-sac. The male and female 

 pro-nuclei come in contact near the upper 

 end of the oosphere and move towards its 

 base. Fusion is complete about the time 

 the base is reached. The young pro-embry& 

 consists of four tiers of four cells each, the 

 upper tier lying free in the archegonium. 



