1go BOTANICAL GAZETTE [SEPTEMBER 
Fic. 45. Section of female gametophyte whose vesicle has five nuclei and 
no cell walls. The exospore has grown to the size of the megasporangium as 
shown in fig. 78. The median layer has divided into the endospore (rep- 
resented in section as a broad black band), and the mesospore which can be 
distinguished only as a delicate layer (represented by a single line) just with- 
out the endospore. The exuspore is of spongy appearance and is still in 
contact with the persistent spore mother cell membrane. Fluid, presumably 
protoplasmic in nature, fills intervening spaces. 
1G. 46. A transverse median section of a female gametophyte in “film” 
stage. The megaspore, endospore and protoplasmic vesicle (studded in its 
apical region with large free nuclei) have stretched to the dimensions of the 
exospore, against whose inner surface they form a layer consisting of three 
delicate lamellae. The central vacuole is filled with clear fluid. The same 
stage is shown in figs. g7 and g8 the former representing a surface view, the 
latter a median section. 
PLATE VII, Selaginella apus. ‘ 
All figures except 56 and 58 drawn with oc. 2, obj. }. Fig. 56 is drawn 
with same combination as plate V; fig. 58 with oc. 2, obj. }. ) 
1G. 47. Surface view of the protoplasmic vesicle as if seen through 
spore walls. 
1G. 48. Vertical median section of the same stage. The nuclei are 
massed in the apical region and the interior of the vesicle is occupied by 4 
vacuole. 
1G. 49. Surface view of the gametophyte at the moment when proto- 
plasmic fibrillae appear in the apical region and radiate over the surface of 
the gametophyte. The nuclei in the lower part of the figure are in process 
of division. The vesicle has increased in thickness (cf. fig.50), and is beset 
with proteid granules. Contents of vacuole a homogeneous liquid. 
1G. 50. Median section of same. 
Fic. 51. Median vertical section of female gametophyte. -Protoplasmic 
vesicle much thicker in apical region where the nuclei are disposed in several 
layers diminishing to a single one in the equatorial region. Fibrillae per- 
meating the nucleated portion have outlined indefinite areas but there are no 
cell walls, Contents of vacuole an emulsion. 
Fie, 52. Section showing a portion of the megasporangium with female 
gametophyte iw situ to show the differentiation of the wall. In the lower- 
most part of the figure the fragile cells of the area of dehiscence are seen 10 
cross section. The inner layer of the wall probably supplies the outer with 
nourishment. The vestiges of the tapetum are ‘upon its inner face, as a 
pavement layer, and a few sterile mother cells lie at the left next the wall. 
1G. 53. Vertical median section of female gametophyte showing the 
differentiation of cells into an apical superficial layer from which develop 
