472 Harper. — Cell- Division in Sporangia and Asci. 
Rothert 1 gives a very full account of the formation of the 
basal septum of the sporangium. He finds that the dense 
protoplasm at the apex of the sporangiophore excretes a 
hyaline plasma in the region where the septum is to be formed. 
This hyaline mass is at first in the form of a ring which 
gradually widens and cuts off the sporangium. It is sharply 
bounded below and passes gradually into the dense plasma 
above. It may be thicker than the breadth of the sporangium 
at that point. A few seconds suffices for the process of building 
this zone. The lower part of the hyaline zone condenses next to 
a cross-wall without sharp contours at first. Cellulin granules 
are abundant in this region, and are dissolved in the hyaloplasm 
and used to form the wall. 
Pringsheim 2 had already pointed out a similar participation 
of cellulin bodies in the formation of cell-walls. 
In sporangia which are full of protoplasm, Rothert finds 
that the hyaline disk may be built simultaneously across the 
entire diameter of the hypha. Cleavage occurs in sporangia 
with a central vacuole by clefts which extend from the vacuole 
outward. They are not formed by a gradual progressive 
splitting, but simultaneously in their entire depth. These 
clefts become connected to form a continuous net. They 
contain cell-sap and not slime, and divide the protoplasm into 
polygonal areas of equal size. The net appears simultaneously 
throughout the sporangium. The plasma is not first divided 
into larger and then progressively smaller portions. At first 
numerous protoplasmic connexions are present between the 
spores, but these soon disappear for the most part. 
In full sporangia the process is the same, except that clefts 
appear in the midst of the protoplasm and are enclosed by it 
on all sides. In sporangia with little protoplasm aggregation 
occurs at certain points as in the case of the oogonia. The 
polygonal masses which are to form the spores now begin to 
contract and round up, but are still connected next the 
1 Die Entwicklung der Sporangien bei den Saprolegnieen. Beitr. zur Biologie 
der Pflanzen, Bd. v, p. 291, 1892. 
2 Ber. d. D. Bot, Gesellsch., Bd. i, p. 303, 1883. 
