Campbell. — Studies on the Araceae. 677 
(Fig. 34 a), a single layer of root-cap cells could be seen, 
but the tissues of the root-apex show very little evidence 
of a definite arrangement, and the same is true of the stem- 
apex (b), whose exact position it is impossible to determine. 
Aglaonema pictum. 
A brief examination was made of A. pictum , which closely 
resembles in general appearance A. commutatum , but which 
shows notable differences in the development of the ovule. 
The cells of the ovule are decidedly smaller, with correspond- 
ingly small nuclei, so that the two species are readily dis- 
tinguishable in this way. More important, however, is the 
marked difference in the development of the embryo-sac. 
So far as one can judge from an examination of a consider- 
able number of mature embryo-sacs of A. pictum, this species 
shows none of the variability so characteristic of A . com- 
mutatum. In all the specimens examined, the embryo-sac 
was not essentially different from other typical Angiosperms. 
The hemispherical egg-cell was accompanied by two large 
and conspicuous synergidae. Small but perfectly character- 
istic antipodal cells were at the base of the sac, and a single 
large endosperm-nucleus, evidently the product of the fusion 
of two polar nuclei, was conspicuous. Numerous starch 
granules were present in the sac, especially around the 
endosperm-nucleus — a not unusual feature of the embryo- 
sac in some other Araceae, e. g. Dieffenbachia. Except for 
the slightly lateral position of the egg-apparatus, A. pictum 
conforms entirely to the ordinary angiospermous type, and 
it is very remarkable that the apparently closely related 
A. commutatum should show such an extraordinary difference 
in the development of the embryo-sac. 
The ripe pollen-spores of A. pictum contain two generative 
nuclei, in which respect they differ from those of Dieffenbachia 
seguine , where there is but a single generative nucleus. 
Symplocarpus 1 also shows but a single generative nucleus 
in the ripe spore. 
1 Duggar, Bot. Gazette, xxix, Feb. 1900. 
