5 1 6 Harper . — Cell- Division in Sporangia and Asci. 
eight nuclei in the ascus proceed as far as the formation of 
a nuclear membrane and the appearance of the nucleolus, 
before the metamorphosis of the aster into the plasma-mem- 
brane of the spore is completed, whereas in the other forms 
the delimitation of the spore is accomplished while its nucleus 
is still in the densely aggregated stage with no nuclear mem- 
brane yet formed. In this Lachnea more nearly resembles 
Erysiphe . It will be seen, however, that Lachnea really 
occupies in this respect an intermediate position between the 
other two Discomycetes mentioned and Erysiphe , since in 
reality the daughter nuclei are not completely developed in 
Lachnea at the time when the spores are completely delimited, 
but increase in size later, as is seen by comparing Figs. 43 
and 46. Such differences as this are doubtless adaptations to 
particular growth-conditions in the different genera. As was 
suggested before, the habit of producing successive series of 
asci in brief periods when external conditions are favourable 
may have led to the modification of the process in the 
Discomycetes as compared with Erysiphe . 
Summary. 
If we compare now the methods of spore-formation in the 
ascus and in the sporangia studied, the differences in the two 
cases are at once apparent. In the ascus, as in the higher 
plants, the cutting out of the daughter cell from the mother 
cell is effected by the agency of the same fibrous kinoplasmic 
elements as were concerned in the division of the nucleus. In 
the higher plants the flat cell-plate is formed by the ‘ cone- 
principal ’ of the karyokinetic figure as named by Van Beneden, 
while in the ascus the daughter cell is cut out of the proto- 
plasm of the mother cell by an ellipsoidal cell plate formed 
from the fibres of the antipodal cone. In this process the 
daughter cell is cut out of the interior of the protoplasm of 
the mother cell, so that it remains surrounded on all sides by 
the material of the mother cell. The daughter cells do not 
