KING: CYTOLOGY OF ARAIOSPORA PULCHRA. 
221 ) 
Although there is no receptive papilla nor other evidence of differ¬ 
entiation at this early stage, yet when these changes take place, 
radial walls will be formed near the edges of this strand and the 
part within will be differentiated as ooplasm and that without as 
periplasm. The writer knows of no other Phycomycete in which 
tube formation by the oogonium has been described. In Araiospora 
there is undoubted evidence that this thick walled tube is formed 
by the periplasm just previous to fertilization. 
It may be mentioned in this connection, that according to Wager 
( ! 96, p. 306) Zalewski observed in the genus Cystopus that “the 
fertilizing tube of the antheridium also becomes surrounded by a 
thick exospore.” Furthermore, Wager (’96, fig. 27) represents a 
persistent fertilization tube on which are formed configurations 
similar to those of the mature oospore. The writer has also seen 
this persistent fertilization tube in Albugo Candida which it is possi¬ 
ble may be, in part at least, of oogonial origin. The presence of a 
wall separating oospore and periplasm, that can be traced out to 
the oogonial wall adjacent to the antheridium, and the appearance 
of similar configurations on the walls of the tube and the outer sur¬ 
face of the oogonial wall certainly suggests a common periplasmic 
origin of the walls of tube and oospore. 
At this point when the tube is formed, Araiospora apparently 
differs from all other investigated Phycomycetes. All observers 
with the possible exception of Trow and Miyake have found that 
the antheridium sends a tube into the oogonium and oosphere. 
Wager, Berlese, Stevens, and Davis have all seen and figured this 
tube in various stages of development. 
The writer has seen no trace of such a tube although he has 
examined hundreds of sections of oogonia seen in all planes and at 
various stages of development for evidences of its presence. After 
the perforation which in Araiospora establishes complete communi¬ 
cation between the two organs, it is only necessary in order to 
bring about fertilization, for the sperm nucleus and some cytoplasm 
to pass from the antheridium into the oosphere. 
We have then in Araiospora, a Phycomycete whose oogonium 
not only makes the perforation between egg and antheridial contents, 
but, in addition, builds entirely a well developed fertilization tube. 
Furthermore, there is here a receptive papilla about the homology 
of which there cannot be the slightest doubt. Instead of being a 
