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BRIEFER ARTICLES 



THE DEVELOPMENT OF THE MACROSPORANGIUM OF 



YUCCA FILAMENTOSA.^ 



Considerable attention has been called to the species of Yucca on 

 account of the curious symbiotism existing between them and the moth 

 {^Profiuba yuccaselld) which is the principal agent in pollinating the 

 stigma (5, 15). The very complete studies of Riley, Trelease, Engel- 

 mann, and others have related to the process of pollination by this 

 moth and the parallel life-histories of the two organisms. My work has 

 been on the embryology of Yucca filamentosa L., and the present paper 

 treats of the development of the macrosporangium. In many points 

 its development does not differ from that of the other Liliaceae which 

 have been the subject of so much embryological research; but there 

 are certain interesting deviations which may or may not be a result of 

 the curious life-history of the plant. 



The material used was' collected in the summer of 1900 from plants 

 growing in the botanical garden of the University of Michigan, and 

 was fixed in Flemming's weaker killing fluid and in Worcester's killing 

 fluid. ^ The ovaries were imbedded in paraffin, sectioned, and stained 

 upon the slide. The haematoxylin stains of Kleinenberg and Hai- 

 denhain and picro-nigrosin were very satisfactory stains for nuclear 

 study, while Zimmermann's fuchsin-iodin-green was the best for gen- 

 eral cytological study. I wish here to acknowledge my indebtedness 

 to Dr. James B. Pollock for criticisms and suggestions. 



The anatropous macrosporangia are arranged in six vertical rows, 

 two in each chamber, arising in acropetal succession from a ridged 

 placenta. A hypodermal cell is early differentiated in the apex of 

 each macrosporangium, from which two kinds of cells later originate. 



'LXV. Contribution from the Botanical Laboratory of the University of Michi- 

 gan. 



"As I am not aware that the formula for Worcester's killing fluid is familiar 

 to cytologists, I give it, as follows : 



Mercuric chlond, saturated aqueous soluti 

 Formalin (40 per cent, formaldehyde) - 

 Acetic acid 10 per cent. 



Formic acid to each liter of solution 

 Wash 



. q6 parts 



4 " 

 . lo •* 



5 drops 



in 70 per cent, alcohol. 



1903] 



209 



