228 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
in Araiospora and their relation to the intervacnolar strands in 
which the cells are formed, have such a striking resemblance to the 
peripheral vacuoles and reticulations in the Peronosporineae (Ber- 
lese, ’97, pi. 7, fig. 3-4), that it suggests a homology between 
these structures. 
The fertilization tube .— In Araiospora, the fertilization tube 
arises in an interesting and novel way. A receptive papilla is 
developed which is essentially similar in structure to those of the 
Peronosporineae. It consists of a deeply staining, fine meshed mass 
of granular cytoplasm just inside the oogonial wall opposite the 
place where the antheridium is appressed, and its function is to 
perforate the intervening walls. Figure 16 (plate 12) represents 
the receptive papilla in the act of establishing connection between 
the sexual organs. The ooplasm just back of the papilla and even 
between the two adjacent peripheral cells, is coarsely vacuolate and 
precisely similar in structure to the ordinary peripheral ooplasm of 
the egg of which it is undoubtedly a part. The apex of the papilla 
as well as the depression which it forms in the oogonial wall are at 
this stage acutely conical. It is, furthermore, hollow as is shown by 
the dark opening at its base (pi. 12, fig. 16). It was stated in 
tracing the development of the oogonium that a layer of peripheral 
cells derived from the periplasm separates the oosphere and the 
original oogonial wall. This separation is complete, except as 
suggested, at the single point where the receptive papilla is formed. 
At this place, the periplasm is cut off from the thread-like ooplasmic 
strand which connects receptive papilla and oosphere proper, by 
radial cell walls of periplasmic origin that are laid down about the 
strands in such a way as to form the fertilization tube. Adjacent 
to this tube, therefore, on all sides is a circle of peripheral cells 
whose walls separate the contents of the tube from those of the 
contiguous peripheral cells. Figure 16 (plate 12) and figure 32 
(plate 15) represent a section showing the tube in the process of 
formation and figures 18, 19, and 20 (plate 13) show later stages in 
its history. In the first figure, fertilization has not taken place as is 
shown by the densely filled antheridium. 
Figure 14 (plate 12) represents an early stage in the origin of 
the fertilization tube. We have here the vacuoles and between 
them the cytoplasmic strands. On the lower side next to the 
antheridium may be seen one of these strands well developed. 
