1921] MACPHERSON—CUSCUTA AND CONVOLVULUS 305 
The stages in the embryo sac of Convolvulus are virtually the 
same, but smaller than in Cuscuta Gronovii (fig. 21). In the 8-celled: 
stage the protoplasm is more dense than that occupying a similar 
position in the 8-celled sac of Cuscuta Gronovii. The synergids 
and egg do not differ much in size as in Cuscuta. The polar nuclei 
and antipodals are of similar appearance, but the polar nuclei, 
usually stand out more prominently than the other nuclei. Here 
also the nucellar cells show evidence of degenerating rapidly. 
Starch grains are present in these cells, but not in the quantities 
in which they are found in Cuscuta. 
The difference in the position of the nuclei in the sac is the 
most noticeable feature. .In Cuscuta the nuclei extend from one 
end of the sac to the other, with protoplasmic connections between, 
while in Convolvulus the nuclei are gathered nearer the micropylar: 
end of the sac, where the protoplasm is aggregated. The first 
division of the fertilized egg in Convolvulus sepium was transverse 
(figs. 22b, 23), and resulted in the formation of an embryo very 
similar to that of Cuscuta Gronovii. The 4- and 8-celled stages 
(figs. 24, 25) were elongated and somewhat irregular in form, and 
much the same as in Cuscuta, but never exhibited the pronounced 
urnlike form. In stages of more than eight cells the embryo of 
Convolvulus is spherical (figs. 27, 29) in form, with a rather pro- 
nounced dermatogen in the majority of cases (figs. 28, 29). The 
embryo continues its growth until in the mature seed it appears 
surrounded by scant endosperm, the two large cotyledons folded 
around the hypocotyl (fig. 30). No stages of the embryo inter- 
mediate between those of the period of development of fig. 29 
and the mature seeds were studied, but these indicate that the 
differentiation into tissues must have been in accord with the 
stages of normal embryonic development. In these advanced 
stages there is a very large suspensor (fig. 27) consisting of large, 
very vacuolated, uninucleate cells, which completely fill the 
micropylar end of the sac and force the embryo well out into the 
sac. The enormous development of the suspensor is much more 
rapid than that of the rest of the embryo, from which its 
separation is not always definite. There is also more endosperm 
than in the corresponding stage of Cuscuta. The endosperm forms 
