Reproduction of Cyst opus Candidus, Ldv. 305 
observation that they appear in summer in from two to three 
hours, but in autumn not until one to two or three days after 
the sporangia have been placed in water. 
His observations on the oospores were made on a Cystopus 
found on the undersides of the leaves of Cirsium arvense. He 
kept sections of the leaf with oospores in a damp chamber, 
but found that the culture could not go on longer than three 
to four days, as after a longer time the oogonia became 
degenerated. In addition therefore to observations made in 
this way, living oogonia in various stages of development 
were observed and drawn at the same time, and the author 
concludes that the exospore is undoubtedly formed from 
the periplasm. As he could only keep them three days, 
he was obliged to begin each third day with different stages, 
so that, as he says, his observations are probably only 
approximately correct. Once only was he able to observe a 
spore for five days. 
In the oogonium, soon after it has become filled with pro- 
toplasm and cut off from the mycelium, the oospore is differ- 
entiated and is surrounded by a thin cellulose membrane. 
In three days more the wall has trebled or quadrupled 
itself in thickness by a deposition of the periplasm. The 
periplasm, shortly after the formation of the membrane 
around the oospore, has a dense, frothy, reticulate appear- 
ance. The vacuoles surrounded by this reticulate protoplasm 
are somewhat angular. They grow considerably while the 
periplasm slowly streams into the meshes towards the wall 
of the oospore in order to form the exospore. The meshes 
break down here and there ; the vacuoles unite with one 
another, and at last the oospore remains suspended to the 
wall of the oogonium by means of a few protoplasmic strands. 
These break through also, and the whole periplasm, or a great 
part of it, falls down upon the wall of the oospore, whilst the 
remainder clings to the wall of the oogonium or floats about 
in the sap and slowly becomes brown and dies. At first the 
wall of the oospore is formed uniformly throughout, but when 
the streaming of the protoplasm becomes more rapid so 
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