On Some Stages in the Life History of Gnetum. 
269 
PLATE XLVIII. 
20. G. africamim. Two cells from the endosperm of an advanced ovule. The one to 
the right is multinucleate, the nuclei showing signs of deterioration. x 720. 
21a. 6r. Gncmon. The lower part of a sac showing multinucleate endosperm com- 
partments. X 720. 
21b The sac from the ovule of fig. 6 more advanced than 2 La. Nuclear fusion has 
occurred in all the endosperm compartments shown. The apparent delay in 
the completion of the endosperm in the micropylar region is probably caused by 
the presence of oospores, x 300. 
22a. G. africanum. The micropylar end of the sac showing three multinucleate 
endosperm compartments (/. ) in which nuclear fusion is in progress. N. Remains 
of nucellar tissue, d. Endosperm-cells produced by division of primary cells 
constituted by nuclear fusion, x 300. 
22 b. a group of fusing nuclei from one of the compartments of 24a. x 1200. 
PLATE XLIX. 
23. G. africanum. Portion of the micropylar end of a sac. Two cells (0.) are pro- 
visionally identified as oospores. Two others above and to the right are more 
doubtful. Groups of sac-nuclei (/.) fairly certainly represent a state preparatory 
to that shown by the compartments (/.) in fig 22a. x 1200. 
24. G. africanum. Micropylar end of sac. 0. Oospore. Endosperm-cells are con- 
tinuous along the sac-wall ; in the centre sej^ation is very irregular, a con- 
dition considered to be due to the presence of this and other oospores, the latter 
not seen in this section. x 500. 
25a. G. africanum. Micropylar end of a sac showing summit of the endosperm. 
N. Crushed nucellus. s.n. Sac-nuclei excluded from fertilisation and from 
incorporation in the endosperm by fusion (c/. Lotsy, 1899, fig. 44, W.o.E.). 
X 160. 
25b. Four of the nuclei (s.«. of fig. 25a). x 1700. 
PLATE L. 
26. G. africanum. Beginning of the formation of the column of small-celled tissue 
near the middle point of the axial line of the endosperm. x 300. 
27. G. africanum. Portions of three proembryonal tubes shown in longitudinal section 
of the endosperm ; one of them is binucleate. x 700. 
28. G. africanum. Distal end of a proembryonal tube containing five free nuclei, of 
which three are seen in the section. x 1200. 
