Miyake, The development of the gametophytes etc. 7 



raeg'aspores are formed from the mother-cell instead of four as it 

 is the case with Sequoia (Shaw, 1896; Lawson, 1904a) and 

 several other Conifers. As the megaspore mother-cell prepares for 

 division, the nucleus is found in the upper part of the cell, and 

 the accumulation of the starch-grains in the lo wer part of the cell 

 is noticeahle (flgs. 37, 39). Froni this as well as from the position 

 of the spindle, as shown in figs. 39 and 30, it can be inferred 

 that the resulting daughter-cells would be unequal in size as was 

 observed by Coker in TaxocUum, although I was not able to find 

 the later stages of the division. The second division was not 

 studied. I am, therefore, not able to determine the number of 

 the Potential megaspores formed, but judging from the position of 

 the spindle of the first division and the figure as shown in flg. 41 

 I am inclined to think that the number would usually be three as it 

 is the case with Taxßdimn. 



The number of potential megaspores formed from a Single 

 mother-cell is not constant even among the members of the same 

 genus. Strasburger (1879) reports that, in Larixeuropea, there 

 are usually three cells formed from the division of a mother-cell. 

 Juel (1900) found four megaspores in Larix sihirica. In Pinus 

 lark'io, Coulter and Chambe riain (1901) find four megaspores, 

 while Miss Ferguson (1904) states that among several species of 

 Pivus the number varies from three to four and the Variation may 

 be found even in the same species, although there is a tendency 

 in some species to form three and in others four cells. In Juni- 

 perus communis (Noren, 1907) the number seems to be usuaUy 

 three and rarely four. the formation of four potential megaspores 

 seems to occur also normally in Sequoia (Shaw, 1896; Lawson 

 1904a), Thnja (Coker, 1904; Lawson, 1907), Libocedrus (Law- 

 son, 1907) and Taxus (Strasburger, 1904; Coker, 1904). 



Development of the Female Gametophyte. 



The lowest of the megaspores now begins to enlarge, and 

 develops into the female prothaUium. The upper sister-cells gra- 

 dually disintegrate and are crowded to the upper corner of the 

 growing megaspore, reraaining for a time as small deeply staining 

 bodies which finally disappear altogether. As the megaspore grows 

 to its füll size, the cytoplasm seems to withdraw from the central 

 portion of the cell by the formation of a large vacuole. The 

 nucleus is found in one side of the cell and imbeds itself in the 

 peripheral layer of cytoplasm (flg. 41). The Organization of the 

 parietal layer of cytoplasm in the one cell stage has been demon- 

 strated by Miss Ferguson (1904) in Pinus. Noren (1907) seems to 

 have observed a similar fact in Juniperus. . 



The nucleus of the megaspore then begins to divido. The 

 free nuclei, formed by the successive divisions, are imbedded in 

 the parietal layer of cytoplasm (figs. 43—46). The division takes 

 place siniultaneously, as it seems to be the rule in the free- 

 nucleated young prothaUium of the Gymnosperms (fig. 47). Miss 



