48 BOTANICAL GAZETTE [yuLy 
dra, in which it has been described by Lanp.® The development 
of the tetrad was observed; and although the early anaphase of the 
first mitosis was not available for the counting of chromosomes, the — 
late prophase of this mitosis and the anaphase of the second mitosis 
showed clearly that the chromosome numbers are 12 and 24. 
SUMMARY 
1. The “antipodal tissue” described by Lorsy as occurring in 
Gnetum Gnemon at the fertilization stage is a sharply differentiated 
nutritive tissue developed in the nucellus beneath the embryo sac, 
which at this stage contains only free nuclei, as described for other 
species of Gnetum. 
2. Embryo formation begins with an excessive, suspensor-like 
elongation of the fertilized egg, accompanied by free nuclear division 
and cleavage walls; and the continuation of free nuclear divisions 
and cleavage walls in the embryonal cell until a multicellular embryo 
is formed. 
3. The endosperm encroaches upon the tissue of the nucellar 
beak with some irregularity, an irregularity which reaches its extreme 
expression in Torreya, with its so-called ‘“‘ruminated” seeds. 
4. The inner integument of the ovule is the morphological equiva- : 
lent of the “inner fleshy layer” of the single integument of other — 
gymnosperms; and the occurrence of two sets of vascular strands — 
is a relatively primitive condition, which has been departed from 
by Ginkgoales and Coniferales. 
5. The chromosome numbers are 12 and 24. 
Tuer UNIversITY oF CHICAGO 
EXPLANATION OF PLATE VII 
Fic, 1.—Embryo sac at an early stage, with centrally placed group of eight 
free nuclei; the cell above, with a large nucleus, is another embryo sac. X50* — 
Fic, 2,—Somewhat later stage of embryo sac (all the nuclei not included); 
showing the beginning of the formation of the pavement tissue; a second em 
sac is also shown. X 500. 
F IG. 2a.—An ovule at an early stage, showing the two integuments and . 
relation of the pavement tissue and embryo sac to the nucellus at the stage show”: 
in fig. 2. X4o. 
°Lanp, W. J. G., Spermatogenesis and oogenesis in Ephedra trijurca. 
GazETTE 38:1-18. pls. I-5. 1904. 
aa 
N 
= 
. 
—— 
Fe 
