744 THE AMERICAN NATURALIST. [VOL. XXXVIII. 



embryo-sac and appropriated as a part of the gametophyte 

 history. 



We can see in these three types of embryo-sac development 

 an evolutionary process of which the third stage is plainly 

 derived from the simpler second and first, and is consequently 

 a highly developed and very complex condition, far removed 

 from primitive gametophyte structures among the angiosperms. 

 The embryo-sacs of these forms (Lilium, Tulipa, Fritillaria, 

 Erythronium, etc.) are probably the most complex spore mother- 

 cells that we know The studies of Schniewind-Thies and 

 Mottier have been supported by other investigations, and more 

 especially by the results of Ernst (: 02) on Paris quadrifolia 

 and Trillium grandiflorum, who followed the history of the 

 heterotypic and homotypic mitoses in these forms in detail. 

 They illustrate the second type of embryo-sac development in 

 the classification of Schniewind-Thies. 



Spindle formation in the embryo-sac mother-cell has not 

 received as much attention as in the pollen mother-cell, probably 

 because material of the latter structures may be obtained much 

 more readily than the former. There have been numerous 

 descriptions and figures of the spindles but few accounts in full 

 of their development. Of the latter the investigation of 

 Mottier ('98) on Lilium is the most complete. This paper was 

 written at the time when the centrosome question was under 

 discussion and served, with other papers on the spore mother- 

 cell (Osterhont, '97, Juel, '97, Mottier, '97) to discredit the pres- 

 ence of these bodies in this structure. Mottier found that the 

 nucleus of the embryo-sac became invested with a close network 

 of fibrillae (Fig. 15 e) from which fibers developed into the cyto- 

 plasm radiating from the nucleus in all directions (Fig. i$f). 

 With the dissolution of the nuclear membrane the fibrillae 

 entered the nuclear cavity, filling it with masses of fibers which 

 gathered into cones to form a complicated multipolar spindle 

 (Fig. 15^). These cones later come together into two poles, 

 but even in the mature spindle the fibrillae are frequently in sev- 

 eral groups at the poles. Essentially the same history is repeated 

 in the second mitosis. A large number of later papers have 

 described and figured multipolar spindles in embryo-sacs, con- 



