44 BOTANICAL GAZETTE [july 



a compact antipodal tissue, sharply distinct from the micropylar 

 chamber with its free nuclei. As a consequence, the embryo sac of 

 G. Gnemon has been used ever since as illustrating a female game- 

 tophyte intermediate in structure between the tissue-filled sacs of 

 Ephedra and Tumboa on the one hand, and the sacs of other species 

 of Gnetum, which contain only free nuclei. Later the same investi- 

 gator in reporting parthenogenesis in G. Ula 3 described the embryo 

 sac of that species as being of the G. Gnemon type. 



Our material of G. Gnemon does not confirm this account. At 

 an early stage of the embryo sac, eight nuclei are observed grouped 

 near the center (fig. i), the sac being invested by the loose tissue of 

 the nucellus. At a somewhat later stage the nucellar cells at the 

 chalazal end of the sac are strikingly differentiated (fig. 2), becoming 

 more and more compactly arranged, gradually obliterating the 

 intercellular spaces, and taking on the appearance of glandular cells. 

 The relation of this tissue in its early stage to the embryo sac is 

 shown in fig. 2a. As vacuolation proceeds in the sac and the free 

 nuclei become parietally placed, this "pavement tissue" becomes 

 more compact and extends deeper into the chalaza (figs. 3, ja). 

 Still later it spreads laterally below, until it becomes fan-shaped in 

 section (figs. 4, 4a), but it is always very distinct in contour and 

 sharply marked off from the surrounding nucellar tissue. At the 

 fertilization stage (figs. 4, 5) the sac contains only free nuclei, which 

 become somewhat grouped at the antipodal end (fig. 5), but there is 

 no walled tissue. Spreading below the sac, however, the mass of 

 nucellar pavement tissue shows a definite contour, which might be 

 merged in imagination with that of the sac and thus mistaken for 

 a compact tissue within the antipodal end of the sac. Lotsy's 

 figures show the real contour of the sac, and his antipodal tissue is 

 clearly this glandular pavement tissue developed in the chalaza. 

 So far as the sac of G. Gnemon is concerned, therefore, its fertiliza- 

 tion stage is that described for other species of Gnetum. It will be 

 noted that after the fertilization stage is reached (fig. 5) the pave- 

 ment tissue begins to lose its glandular character; and later it is 

 destroyed entirely by the growing endosperm. 



3 Lotsy, J. P., Parthenogenesis bei Gnetum Via Brongn. Flora 92:397-404. 

 pis. 9, 10. 1903. 



