1912] SHARP— ORCHID EMBRYO SAC * 375 



Figs. 17 and 18 show two stages in the development of the pro- 



* 



embryo of E. cochleatum. In these three figures is seen the general 

 course followed by the Epidendrum proembryo up to the stage 

 found in the mature seed. Multiplication of cells commences at 

 the chaiazal end of the filament and extends upward, resulting in 

 an oval mass of cells which is still to be regarded as a proembryo, 

 since the body regions have not yet been marked out. 



Epidendrum verrucosum Sw., E. cochleatum L., and E. 



globosum Jacq. 



The embryo sacs of these forms were briefly examined. In 

 the first two species stages were observed corresponding in all 

 essential features to figs. 1, 3, 5, 12, and 14. In E. globosum were 

 seen an ordinary 8-nucleate sac and a stage like that shown in 

 fig. 14. It thus appears that E. 



verrucosum 



formation 



an embryo sac of the usual type from a single megaspore. The 

 investigation of these three additional species was not carried far 



enough to 



methods 



developing the embryo sac or not. 



Phajus grandifolius Lour. 



The early stages in the development of the embryo sac in this 

 form correspond to those described above for those cases of Epiden- 

 drum in which but one megaspore is concerned in the formation 

 of the sac. 



megaspore mother cell (fig. 19) divides 

 daughter cell again divides to form tw( 



The 



outer daughter cell and megaspore disorganize (fig. 20), while 



the inner megaspore 



The 



megaspore 



gives rise to four; two of these lie at each end of the sac, the center 

 of which is occupied by a large vacuole. The two chaiazal nuclei 

 undergo no further division, while those in the micropylar end 

 divide to four (fig. 21), which become organized into an egg appa- 

 ratus of the usual type and a free polar nucleus. This polar 

 migrates toward the base of the sac and lies near the two chaiazal 



