Schwarze: Cleavage in Sporangia 157 



Text figure B, i-ii, represents the lengths and breadths of a 

 sporange at successive stages in spore formation. The micrometer 

 measurements are as follows : 



9 :12 P.M 86 /x long — 26 fx, wide 



9:27 P.M 88 yu, long — 26 ix wide 



9:37 P.M 90 fx long — 25 fx wide 



9:56 P.M 92 fx long — 25 fx wide 



10:05 P.M 93 A* long — 25 ix wide 



10:10 P.M... 94 fx long — 28^, wide 



10:17 P.M 90 ix long — 27 fi wide 



10:22 P.M 92 fx long — 26 ix wide 



10:30 P.M 86^, long — 22 ix wide 



10 :34 P.M. Spores moved to and fro. 



At 10:10 P.M. the sporange had reached its maximum size ; the 

 basal wall was concave, due to the turgor within the sporange. At 

 10:17 P.M. the clefts apparently cut through the plasm membrane, 

 the spore initials rounded up, and the sporange decreased four 

 microns in length and one micron in diameter. The basal wall was 

 now flattened. This stage of contraction was followed by the 

 expansion stage. The spore initials became tightly pressed to- 

 gether, the protoplasm assumed a homogeneous appearance, and 

 the spore outlines were only visible as very faint lines. This is 

 the stage that deceived Strasburger (48), for he writes as follows : 

 "Wiederholt sind mir Falle vorgekommen in welchen nach dem 

 die Sporenanlage es schon bis zur Bildung der Kornergrenzen ja 

 selbst Hautschictgrenzen gebracht hatte, plotzlich die ganze Ent- 

 wickelung riickgangig wurde, alle Trenungsandeutungen schwan- 

 den und das Sporangium alsbald wieder von gleichmassig kam- 

 merigen Protoplasm gefiillt erschien. Dann nach kurzer Zeit, 

 wurde die Entwickelung, und zwar nun auffallend schnell wieder 

 aufgenommen. Eine solche zweite fiel mir, im Verhaltniss zu der 

 Ersten stets durch die grosse Regelmassigkeit der Theilstticke auf /' 



The great expansion following the delimitation of the spore 

 initials, the temporary loss of the granular character of the spore 

 protoplasm, the obscuring of the cell boundaries through close con- 

 tact, and the subsequent contraction which reveals the polygonal 

 spore masses have given rise to much confusion. Butler (9), in 

 1907, speaking of spore formation in Pythium proliferum, writes : 

 " From this I have been led to suppose that even at this stage the 



