396 BOTANICAL GAZETTE [MAY 
more of a lining for the sac than in Cuscuta, and is also associated 
with abundant perisperm in a number of cases (figs. 26, 31). The 
entrance of the pollen tube through the micropyle can easily be 
traced in Convolvulus, although it is not apparent in Cwuscuta. 
The pollen tube remains in Convolvulus (fig. 32a and 6) as late as 
the 4-celled stage of the embryo or later, apparently without being 
ruptured. The actual fusion of the tube and egg nucleus was 
not observed. 
One of the striking points about the embryo of Convolvulus is the 
frequent occurrence of polyembryony. In Cuscuta not one case 
was observed, but in Convolvulus it soon became evident that 
polyembryony was not the exception to the rule, but a usual 
occurrence in the development of the embryo. Polyembryony 
may be observed from the earliest stages until quite a highly devel- 
oped embryo is present. In one case several embryos were lying 
in the micropylar end of the sac, two of them consisting of two 
cells with a 1-celled embryo also present (fig. 22a and 6), and 
8-celled stages with one or more 1- or 2-celled embryos present 
were frequently observed (fig. 25), as were larger embryos that 
had the dermatogen developed (fig. 26). These extra embryos 
never developed at the antipodal end of the sac, and do not appear 
to be formed: by the budding off from the fertilized egg. They 
seem rather to be formed from the synergids, or it may be that 
some of what appear to be 1-celled embryos are rather persistent 
synergids that have not developed any further and have not been 
absorbed. There may be some basis for assuming that polyem- 
bryony is the result of parthenogenesis. 
Summary 
1. Except for the enlargements of undifferentiated tissue on 
the sides of some of the embryos of Cuscuta, there appears to be 
no cotyledonary development. 
2. The development of a large vacuolate suspensor is typical 
of the older embryos of Convoloulus. 
3. Polyembryony is the rule rather than the exception in the 
development of the embryos of Convoloulus. 
