THE FEMALE GAMETOPHYTE 115 



the antipodal cells (Fig. 73H). The basal antipodal cell contained 

 a variable number of nuclei, which subsequently fused to form 1 

 nucleus. Embryo sacs with fewer than 14 nuclei were also seen, 

 but this was due to a degeneration and disappearance of some of 

 the nuclei at the chalazal end. 



In specimen 2, collected from a different locality in Sweden, 

 the megaspore mother cells as well as the developing embryo sacs 

 and their nuclei were found to lie of a larger size than in the first 

 plant. The chalazal megaspore nucleus degenerated soon after its 

 formation. The remaining 3 nuclei divided to form 6 and then 12 

 nuclei. In the mature embryo sac the basal antipodal cell was 

 observed to have more than one nucleus, while the remaining antip- 

 odal cells were uninucleate. 



Material of the same species collected from the Brooklyn Bo- 

 tanical Gardens, New York (Maheshwari and Haque, 1949), showed 

 the usual 4- and 8-nucleate stages, after which all the nuclei were 

 found to divide again, resulting in 16 nuclei, 4 at the micropylar end 

 and 12 at the chalazal. These organize to form a three-celled egg- 

 apparatus, two polar nuclei, and eleven uninucleate antipodal cells. 



The embryo sac of Tanacetum vulgar e (Fagerlind, 1941) is funda- 

 mentally similar to that of Chrysanthemum. The megaspore mother 

 cell (Fig. 74 A) undergoes the usual reduction divisions to produce 

 2 (Fig. 745) and then 4 nuclei (Fig. 74C) which become arranged 

 in a linear fashion (Fig. 74D). Vacuoles soon appear between the 

 nuclei, which now increase in size and prepare for the next division 

 (Fig. 74E), resulting in the formation of 8 nuclei (Fig. 74//"). In 

 many cases, however, the basal nucleus does not take part in the 

 division and soon begins to degenerate (Fig. 74G), and sometimes 

 the subbasal nucleus also remains undivided (Fig. 74F). At this 

 stage the embryo sac may, therefore, contain 8, 7, or only 6 nuclei. 

 If all of them take part in the next division, the mature embryo 

 sacs may be 16-, 14-, or 12-nucleate (Fig. 74/). But frequently 

 there is a further degeneration of one or two of the chalazal nuclei 

 so that embryo sacs with fewer than 12 nuclei are not uncommon 

 (Fig. 74/). 



Crucianella laiifolia (Fagerlind, 1937), a member of the Rubiaceae, 

 also belongs to the Drusa type. After the reduction divisions are 

 over, the coenomegaspore shows a pronounced elongation, rupturing 

 the nucellar epidermis at its micropylar end (Fig. 737). The next 



