5 21 
Black . — 7 /£<? Morphology of Riccia Frostii , -* 4 ^ 5 /. 
Selaginella apus and N. rupestris , finds the protoplasm is in contact with 
the membrane-forming coats at every point. Beer (6), in the same year 
(’ 05 ), supports Fitting’s theory, observing the same condition in Oenothera 
as does Tischler ( 41 ) for Mirabilis Jalapa. Beer ( 7 ) believes that the 
spines and rodlets of pollen-grains of Ipomoca purpurea , Roth., develop 
independently of any direct protoplasmic influence. Beer ( 5 ) describes the 
development of the spores of Riccia glauca as follows: Upon the primary 
spore mother-cell walls secondary and later tertiary thickening layers are 
deposited. The secondary thickening layer is more or less mucilaginous. 
It sometimes separates completely from the primary wall. A plug of 
mucilage was observed just within the first spore wall at the equatorial 
rim. It has no direct relation to the developing layers. The second spore 
wall has three well-defined regions : an external, loosely laminated region, 
within this a dark layer, and an internal, densely laminated region. The 
endospore is formed later. Separating it and the second spore wall, there 
is often present a thin band of material. The protoplast of the spore is 
directly concerned in the development of the spore membrane. 
Whatever the nature of the beginning of the walls in spore tetrads 
of Riccia Frostii may be, later development of the spore coat is accom- 
panied by a close protoplasmic connexion. In general the development 
of the spore coats is similar to that described by Beer for Riccia glauca. 
The immature spore tetrad is shown in Fig. 36, with definite walls 
separating the spores. Inside this wall, which is a thin membrane and 
may be designated according to Miss Lyon as the ‘ mother-cell membrane ’, 
a second layer is formed. This is thicker, stains faintly with gentian 
violet, and appears of a gelatinous nature. It is connected by homogeneous 
strands, which appear to be of the same nature as the cytoplasm collected 
around the nucleus. The nuclei are small and contain usually one large 
and one or more smaller nucleoli embedded in a delicate reticulum. In 
Fig. 37 the cytoplasm appears more granular, and is seen extending in 
strands to all parts of the spore wall. Inside of the homogeneous gelatinous 
layer, and projecting into it in numerous small points, a layer develops 
which ultimately becomes the rough outer coat of the spore. The beginning 
of another layer is also distinguished inside of it. In the next figure (Fig. 38) 
the projections have become more pronounced. The layer inside this 
appears striated. This layer corresponds to the second spore wall in 
R. glauca described by Beer. Eventually the endospore is formed. The 
developing exospore is yellow, then orange, and finally black. The sculp- 
turing of this outer coat is shown in Fig. 39 in a surface view of a spore, 
and the projections correspond to cross-sections of an irregular system of 
ridges. No spores were observed except in the tetrad form, and the 
triangular appearance may not be characteristic of the individual spore. 
The plug of mucilage described by Beer for R. glauca was not observed in 
