1905] LYON—THE SPORE COATS OF SELAGINELLA 287 
tact at every point with the thick gelatinous membrane from which 
the coats are formed. 
The megaspore mother cell in all species may be distinguished 
from the other sporogenous cells (fig. 1) at the time that the sporan- 
gium wall is differentiated into three layers. It is slightly larger, 
more granular, and stains intensely as contrasted with its sister cells. 
Its wall thickens slightly, stretching and probably growing some- 
what, and persists until the enclosed spores are more than half grown. 
I shall refer to it as the mother cell membrane, to distinguish it from a 
second membrane, the spore membrane, that shortly appears upon 
its inner surface in contact with the protoplasm (fig. 1). The mother 
cell membrane remains comparatively thin; whereas the spore 
membrane is gelatinous in nature, becomes very massive, and dis- 
solves readily in many of the fixing reagents, especially in very young 
Stages. It increases rapidly in bulk, forming a thick layer about 
the protoplast which for a period grows imperceptibly, if at all (jig. 2). 
As the mother cell divides, it assumes a dumb-bell shape, the two 
resulting Spores often not completely separating from each other 
until half grown (jig. 3). At this early stage, each spore consists of 
. Protoplast with a relatively large nucleus, and an envelop of thick 
gelatinous Matter, the spore membrane. The two spores lie within 
- mother cell membrane. Whether any part of the spore membrane 
's formed in connection with a nuclear plate at the time of cell division 
Hes 2% ne determined, owing to the diminutive size of the spindles 
a infrequency in the material investigated. The protoplast 
bia vacuolate. Many small vacuoles ultimately coalesce to 
oi ugd large one centrally placed, so that the protoplast comes 
a delicate vesicle (fig. 4). 
os =a Com of a coat is detected as a transformation of a 
: € gelatinous spore membrane. A clear homogeneous 
= little distance from the protoplast stands out in con- 
. ey rest of the membrane, which has become granular (fig. 4)- 
mie... becomes convoluted upon its outer surface, and these 
of the me ° ee giai with radiations in the outer granular wee 
solutions Tane that suggest fixed diffusion currents (fig. 4) ) 
At this Passing through the two membranes from the sporangium. 
"ime, the sporangium is turgid with fluid made up of dis- 
