228 BOTANICAL GAZETTE [MARCH 
common, the failure occurring either directly after synapsis, the chromatin thread 
not being segmented into chromosomes, or after tetrad formation, the spores 
aborting. The microsporangiate archesporium consists of a hypodermal plate of - 
cells (two cells in transverse section and six in longitudinal). In connection with 
the reduction division, 20 chromosomes were counted as the gametophyte number; 
and this was checked up by an approximate count of 4o in certain nuclear divi- 
sions of the embryo. The solitary megaspore mother cell is differentiated 
beneath a heavy development of nucellar tissue (about 12 layers). One of the 
surprising results is that the functioning megaspore of the linear tetrad is the 
micropylar one. The antipodal cells are evanescent, and the fusion of the polar 
nuclei is somewhat tardy. Double fertilization was observed very distinctly. 
. In the development of the embryo no suspensor was discovered, and before the 
segmentation of the fertilized egg about roo free, parietally placed, endosperm 
nuclei have appeared. Later there is endosperm wall-formation, and in the 
later stages of the embryo it is imbedded in a delicate endosperm tissue. Perhaps 
the most interesting data are those in reference to the time-relations of these 
events, the rate of development being unusually high. Flowers hand-pollinated 
at 10:00 A. M. showed fertilized eggs in the afternoon of the following day. The 
interval between megaspore-formation and the completed sac (fertilization stage) 
is three days. About 60 hours after fertilization (33 days after pollination) the 
egg segments, and in about a week after pollination the embryo consists of “hun- 
dreds of cells.”—J. M. C. 
Pteridosperms and angiosperms.—OLivER has published the substance of a 
lecture delivered before the Botanical Club of Cambridge University?’ and illus- 
trated it by a scheme of the occurrence of vascular plants in geological time, 
modified from E. W. Berry. It discusses the bearing of recent investigations of 
the pteridosperms and cycads on the origin of seed-plants. Attention is called to 
the fact that the appearance of the Cycadophyta is geologically synchronous with 
the disappearance of the pteridosperms, and that the former perpetuate in many 
respects, especially in the cycadeoidean forms recently described by WIELAND, 
the fern-like characters of the latter. Just as the incoming of the Cycadophyta 
marks the end of the reign of the pteridospermic gymnosperms, so the appearance 
of the angiosperms in the Cretaceous and Tertiary marks the waning of the 
Cycadophyta. The author calls attention to the angiospermoid protection of the- 
exalbuminous seeds of Cycadeoidea by the sterile scales of the inflorescence. 
He further emphasizes the resemblance of the bisporangiate inflorescence with its 
perianth-like envelops in Cycadeoidea with the typical angiospermous flower, 
since the parts occur in the same order, namel perianth, microsporophylls, and, 
uppermost of all, the megasporophylls. He suggests that possibly the Cycado- 
phyta may be appropriately divided into two series, the Gymnocycads and the 
Angiocycads, the former the ancestors of the living cycads and the latter consti- 
= OLIVER, F. W., Pteridosperms and angiosperms. New Phytologist 5:232-242- 
1906. 
