Mar. 8, 1924 
Aecidiospore Discharge in Relation to Spore Wall 
755 
brown at first, then blue, with iodin. While in this condition the 
papillae superficially resemble very closely the striated germ pore plugs 
of the Myrica rust being considered here; they are of an entirely different 
origin and not to be compared, except as to location, with respect to the 
germ pores. The lids or caps which cover the germ pores in Cucurbita 
pollen (Strasburger ( 8 ), fig. 77-84) are more nearly analogous because 
the lids are developed out of the exospore layer. Had the caps developed 
beneath and not out of the original cell wall, they could be said to be 
homologous to the exospore thickenings of aecidiospores and of zygo¬ 
spores of the Mucoraceae. 
Vuillemin (9) who studied the development of the walls of zygospores 
of Sporodinia and other Mucoraceae, recognizes five different layers or 
membranes. The innermost layer is composed of a granular matrix. 
The next part of the wall is referred to as the cartilaginous layer. This 
is bordered by a middle, thin membrane. The fourth layer is usually 
heavily carbonized and developed into- characteristic warts or spines. 
Surrounding the young zygospore is the thin membrane, originally the 
primitive wall of the progametes. 
Dangeard ( 2 ) features the two membranes which are easily separated. 
The exospore, warted and carbonized, originates as a separate cone- 
shaped thickening beneath the thin outer membrane. The endospore is 
the thick layer within which follows the undulations of the exospore. 
Lendner (6), Moreau (7), and others studying zygospore formation also 
show that in several species the warts or thickenings originate as separate 
cone or dome shaped structures in a matrix and by lateral extention fuse 
together to form the firm carbonized layer of the spore wall. Without 
lies the primitive membrane of the gametangia; within there remains a 
separable membrane of considerable thickness in contact with the cyto¬ 
plasmic contents of the zygospore. Disregarding the outer thin layer 
of the young spore wall which is usually not to be distinguished in the 
mature spore, the two remaining layers are referred to as “exospore” 
and “endospore”. 
The pore plugs in the aecidiospore of the bayberry rust develop in the 
matrix or layer out of which the thick warty or echinulate exospore is 
formed but outside of this heavy wall, what the writer has interpreted 
as the thin primitive membrane of the spore wall can be seen if the 
spore cells are plasmolized. The inner membrane then also becomes 
visible. 
As noted above, Dietel has shown that sporidia from certain teleuto- 
spores are sometimes projected 0.6 to 0.8 mm. The writer has made no 
attempt to learn just how far a spore can be thrown as it is discharged 
from the aecidium. The spore print (fig. 1) shows that every spore is 
forcibly expelled; there is always a clear space around the mouth of 
the cup where no spores have fallen. Not many spores are projected 
a distance of over one hundred times their diameter when an aecidium 
is laid directly on a glass. As the diameter of an aecidium is only a few 
times that of a spore, it can be seen that a spore has not long to fall 
before it hits the glass. Spores shot from aecidia growing horizontally 
on buds or coiled leaves would certainly be scattered much farther and 
more efficiently if they were given an initial horizontal velocity. 
Germ pores of certain teleutospoires are very commonly figured as 
being covered by very delicately bounded papillae. Structures like the 
papillae in the geranium pollen represent in part extruded cell sap os 
cell contents. The pore plugs are persistent morphological structurer 
