746 Wisconsin Academy of Sciences, Arts, and Letters. 
plasm is actually separated from tlie epiplasm, the center 
breaks away from the plasma membrane and the beak of the 
nucleus is slowly drawn in. There remain traces of the fibers 
which did not take part in the fusion, but these soon disappear 
(Fig. 15). While resuming its normal spherical shape, the 
nucleus moves down into the center of the spore mass and lies 
there in a resting condition, the chromatin in an irregular re¬ 
ticulum .always oriented on the large center (Fig. 16). 
Between the spore membrane and the surrounding proto¬ 
plasm, a space appears in which the spore wall is finally de¬ 
posited. The epiplasm is often thickened along this space, but 
still has no limiting membrane. The spore wall is at first 
a faint blue line (Fig. 16), but when completed it is a thick, 
dense coat, and the epiplasm is no longer drawn back from it. 
With the ripening of the spores the perithecium reaches its 
maturity. The dark, thick walls of the cells on the upper sur¬ 
face have become so hard and brittle that they invariably break 
in sectioning, while the cells on the under side retain their thin 
walls and appear in normal living condition. How much this 
differentiation is due to the drying out of the upper exposed 
surface of the fruit body, while the lower cells are protected 
from too great loss of moisture, could only be estimated by 
comparison with other mildews ; however, Erysiphe and Phyl- 
lactinia give np evidence on this point, and FTeger’s view (21, 
22) as to the functional difference may be accepted for the 
present. The appendages grow to great length and branch 
profusely at their extremities. They contain protoplasm and 
a large elongated nucleus which iies just below the dichoto- 
mously branched end. The walls, though thin and transpar¬ 
ent-, are very brittle. 
GENERAL CONCLUSIONS. 
All the stages in the life history of Microsphaera thus far 
studied show that the central body is a permanent structure of 
the nucleus, and that it is present not only as a definitely dif¬ 
ferentiated body, but also as a point of -attachment for the chro¬ 
matin. 
The central body is nowhere more easily demonstrated than 
