1910) TWISS—PROTHALLIA OF ANEIMIA AND LYGODIUM 173 
coat adhere to it (jig. 4), but for some time not very tightly, so that 
they are easily pulled away in the cutting. The protoplasm comes 
to form a delicate continuous sheet between the granules and over 
their surface (fig. 5). The mature wall shows that the protuberances 
thus formed are still of varying sizes and somewhat irregularly placed, 
and that they and the exposed position of the exine are covered by 
- the thin layer of cytoplasm (fig. 6). In the spores of Lygodium 
circinatum (figs. 7, 8), sections in which the coats have been broken 
apart in the cutting show clearly the delicate intine (7), the heavy 
exine (ex) with its two differently staining portions, and the epispore 
(e) of heavy projections formed by the tapetal protoplasm. It is 
probable that in this episporé we have merely a difference in degree 
from the more delicate one reported for Filicineae. If the granules 
were not developed, we should have in the thin sheet of protoplasm 
covering the spores just such an epispore. 
DEVELOPMENT OF THALLUS 
The exine of the spores is opaque, so that it was difficult to deter- 
mine just when chlorophyll was formed. The first definite signs 
of germination are visible in five to seven days, when the spore coats 
split and a colorless cell, the first rhizoid, protudes (fig. 9, a). The 
first prothallial cell may be seen as a projecting papilla soon after 
the rhizoid, but seems to grow more slowly, so that by the time it is 
well out of the spore the rhizoid is five or six times the longer 
(fig. 12). Very shortly there is seen a smaller papilla pushing from 
the spore at the side of the first (fig. 10, p*), and as the two protrude 
farther it becomes clear that the smaller one is a cell cut off from the 
side of the larger, and that the rhizoid has its origin in turn from this 
smaller cell (fig. 12). The first division of the spore does not separate 
the rhizoid and first prothallial cell. 
The chlorophyll grains are fewer in number and smaller than those 
in the larger cell, where they are crowded in a dense mass about the 
nucleus. Sometimes two rhizoids appear, as BuRcK reports is 
always the case in L. japonicum, but this seems to happen rarely. 
Even more seldom the prothallial cell emerges before the rhizoid. 
The three layers of the spore coat may be distinguished at this stage 
(figs. 9, 1 0). It is not at all unusual for a spore to produce two fila- 
