EMBRYO DEVELOPMENT AND POLYEMBRYONY 
Taxodineae 
Among Taxodineae, the excessive cleavage polyembryony described for 
Sciadopitys becomes reduced, as illustrated by Taxodium (9) (figs. 41-45). 
Figure 43 doubtless represents two unequal tiers of embryo initials in 
addition to the upper aborting nuclei. The lowest tier forms separate 
embryos (fig. 44), while the next tier of initials above it forms suspensor 
Figs. 41-45. Stages in embryogeny of Taxodium distichum, X 200. After Coker (9). 
cells. Cleavage polyembryony is apparent. It is probably the normal 
condition, and we sometimes have the organization of embryo initials 
after the first appearance of walls, as shown in figure 42. Coker shows the 
order in which the walls appear in the embryos of figure 44, which is a good 
start for an apical cell stage. In general the embryo of Taxodium shows 
great similarity to that of Finns, except for the unequal organization of the 
tiers in the proembryo (see figs. 41 and 43) and the absence of the rosette 
cells. 
Cunninghamia (28) may be a step higher, for here it is highly probable 
(judging from the few stages described by Miyake (figs. 46-51)) that only 
the lowest embryo initial gives rise to the embryo. This may have been 
the method of overcoming cleavage polyembryony in this line of evolution. 
Figs. 46-51. Stages in embryogeny of Cunninghamia sinensis, X no. After Miyake 
(28). 
