Sporangia and Spores of Aneimia phylhtidis . 1063 
of the spore, either from plasmolysis caused by the reagents or from natural 
causes. The balled-up condition of the nucleus in Fig. 20 indicates that the 
former alternative is the more probable. 
We find in the literature speculations as to how the growth in thickness 
of spore coats comes about. In Helminthostachys , Beer, 1 . c., found that the 
spore protoplast, at the time when the exospore first appeared, was so poor 
in substance as to make it unlikely that this could be employed in the 
growth of the wall. The protoplastic substance of Aneimia spores also is 
very little, even relatively less than in the spores of Helminthostachys 
(compare my Figs. 18 and 20 with Beer’s Fig. 11), and entirely inadequate, 
it seems to me, to supply materials for the increase in wall thickness that 
takes place between the stages represented in Figs. 18 and 20. As Beer 
suggests, it appears that the substance for this increase must come from, or 
through the agency of, the tapetal cytoplasm. Fitting (’00) comes to 
a similar conclusion for the spores of Isoetes and Selaginella. Beer holds 
it impossible to decide whether this material is applied to the wall by the 
plasmodium or by the spore protoplast. He suggests that in the latter 
event the nutrient substance would have to enter the spore protoplast in 
liquid form before it could be applied to wall construction. As was stated 
above, in Aneimia the exospore takes the safranin stain strongly while it is 
yet quite thin. This reaction, according to Thomson ( 05 ), indicates that 
the exospore has undergone the cutin or suberin modification ; and this 
would make difficult the passage of materials to and from the spore proto¬ 
plast. This fact adds plausibility to the theory that the plasmodium, 
working from without, supplies the materials, and possibly the stimuli also, 
for the characteristic growth of the wall. 
In his studies of various species of Isoetes and Selaginella , Fitting, 1 . c., 
finds the exospore widely separated from the mesospore and the spore 
protoplast withdrawn from contact with the latter, excepting at the spore 
apex, before these coats have attained their characteristic thickness, and 
before the endospore has been laid down. Although he finds no indication 
of protoplasm inhabiting the spore coats, he nevertheless comes to the 
conclusion that these have the power of constructing their own substance 
from the materials that come to them from the tapetum. He says: ‘ Ich 
glaube also, dass gewichtige Grlinde zu der Annahme vorliegen, dass die 
neuen Hauttheilchen erst innerhalb der wachsenden Membranen entstehen 
oder, mit anderen Worten, dass diese Membranen die Fahigkeit besitzen, 
ihre constituirenden Verbindungen selbst aus einer Nahrlosung aufzubauen.’ 
And again : ‘ Ich halte es fur denkbar, ja flir wahrscheinlich, dass die 
Sporenhaute von Isoetes und Selaginella nicht von dem Sporenplasma aus, 
sondern direct von den Tapetenzellen ernahrt werden.’ 
A more recent study of Selaginella by Florence Lyon (’ 05 ) suggests, 
however, that where gaps occurred between the membranes and spore 
