The Biology of Polyporus Pargamenus Fries 63 
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Microscopic examination shows each spore to be a color- 
less, unicellular body measuring 5—6.5 microns long by 
2—2.25 microns broad, the protoplasmic contents of which 
are homogeneous and usually devoid of vacuoles. In the 
spores of Polyporus pargamenus we distinguish first a base 
(Fig. 2, A), the point at which the spores are attached to the 
sterigmata and at which their abcission occurs at maturity." 
The organic center of the base is the apiculus (a), which is 
usually situated excentrically and as a general rule does not 
coincide with the geometric center (x). The organic center 
of the top is the apex (y), which coincides with the geometric 
center. The line (ay) which joins the apiculus “with the 
apex is the organic spore-axis. The line (xy) which joins 
the geometric ‘center of the base with the apex is the geo- 
metric spore-axis. The symmetry plane (qq) running trans-: 
versely through the spore at the central point (c) of the 
geometric axis 1s to be regarded as the spore cross-section. 
As seen from the base and apex, every basidiospore is 
oriented in a definite manner, and we distinguish therefore 
four surfaces: a dorsal and a ventral side as well as a right 
and left lateral surface. The spores on their basidia are 
directed with their dorsal surfaces toward the outside and 
with their ventral surfaces toward the inside, while they 
limit one another laterally with a side surface. The dorsal 
and ventral sides are divisible into two symmetrical surfaces 
by a basipetally running symmetry line (Fig. 2, B) (xy). 
The plane formed by the union of the dorsal and ventral 
sides is the bilateral symmetry plane which divides the spore 
accordingly into two symmetrical halves, a left lateral (1) 
and a right lateral (r) part. This is the only symmetry 
plane always possessed by each basidiospore. 
A plane running through the geometric center at right 
angles to the bilateral section guile the dorsal and ventral 
sides, the dorsiventral section (Fig. 2, A) (xy), divides the 
spore into a dorsal and a ventral spore half which are never 
“The form of the geometrical description of the basidiospores is based 
upon that given by Falck (1909, pp. 76-79) for the spores of species of 
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senzites. 
