428 BOTANICAL GAZETTE [may 



conclusions being based on the fact that the haustoria are always 

 found in contact with parts which are well supplied with nourish- 

 ment. Miss Balicka-Iwanowska disagrees with Hegelmaier 

 (7) as to the function of the tapetum. Hegelmaier beheved it to 

 act as a protective covering, while the former seemed to prove that 

 it serves to pass nutritive substances on to the embryo sac, and 

 that it possibly has a digestive function, since the cells of the integu- 

 ment adjoining it are found constantly breaking down. In 1906 

 ScHMiD (12) investigated numerous species of the Scrophulariaceae. 

 He discusses the formation of the embryo sac, fertilization, endo- 

 sperm formation, and the development of the haustoria. He has 

 done very little with the development of the embryo. In 191 5 

 Miss Mitchell (id) investigated the embryo sac and the embryo 

 in Striga lutea, a semi-parasitic plant found in South Africa. In 

 this form she has noted the lack of a tapetal layer. 



The material for this study was collected near Boulder, Colo- 

 rado, where the species is abundant. The indeterminate inflores- 

 cence affords flowers in all stages of development on the same plant. 

 Such material was killed in chrom-acetic acid, cut in paraffin, and 

 stained in various stains, safranin-gentian violet proving the best. 

 Longitudinal sections 10 m thick proved quite satisfactory for 



study. 



The writer is indebted to Dr. Francis Ramaley of the Uni- 

 versity of Colorado for advice during the early stages of the work, 

 and especially to Dr. Charles J. Chamberlain of this laboratory, 

 under whose direction the work was completed, for his kindly aid 



and criticism. 



Ovary and embryo sac 



The ovary of Pentstemon secundifloriis Benth. is of the ordinary 

 bilocular scrophulariaceous type, with the partition somewhat 

 swollen in the median Hne forming the placenta, which bears the 

 numerous crowded anatropous ovules. Longitudinal sections of 

 such an ovary at right angles to the partition afford a large number 

 of ovules in each section for study. Sections of very young ovaries 

 show the ovules beginning as slight swellings of the placenta. The 

 megaspore mother cell is not distinguishable in such an early stage, 

 becoming apparent only after the beginning of integument forma- 



