72 THE SAPEOLEGNIACE^ OP THE U^SIITED STATES, 



clear that Rothcrt's explanation 18 the correct one, since, as the clefts broaden, the 

 granules disappear, or separate with the origins. 



At about the same time, with the appearance of the first signs of the segregation 

 of the spore origins, there is formed, if the sporangium belong to a species of Aclilya 

 or Saprolegnia, normally at its apex, an outgrowth or papilla, from whose tip the 

 zoospores will finally escape. Its formation begins with the accnmulation at that 

 point of a mass of hyaloplasm which presses the wall outward. After its formation, 

 the hyaloplasm becomes granular, except a thin layer which remains intimately con- 

 nected with the apex of the papilla (Fig. 7, a). This apical wall is always less 

 sharply defined and more highly refractive than any other part of the sporangial 

 wall, and these characteristics become more and more prominent until the escape of 

 the spores. 



The clefts between the spore origins rapidly widen and deepen, causing the con- 

 necting threads to become broken and withdrawn into the bodies of the origins. In 

 view of subsequent changes, and of what seems the most reasonable explanation of 

 them, it does not appear probable that the clefts extend at once completely to the 

 outer wall, although it is often very difficult or even impossible to detect with high 

 powers and excellent material any protoplasmic lining of the wall at this stage, when 

 the spore origins are most widely separated. Another good reason for believing that 

 the origins are still connected by a delicate parietal lining may be found in the fact 

 that the whole surface of an origin next to the wall remains closely aj)plied to it 

 throughout this stage, and does not become rounded off at the corners, as happens 

 on the other sides of the origin, and on this side at a later stage. 



After the separation of the spore origins has become nearly complete, there fol- 

 lows suddenly and without warning the so-called "homogeneous" stage of Biisgen, 

 the "stage of swelling of the spores" of Rothert. The spaces between the spore 

 origins disappear by the apparent swelling up and fusion of the separate origins, and 

 the contents of the sporangium appear less opaque and less granular than before. In 

 spots corresponding approximately to the middles of the spore origins are to be seen 

 clear, bright spots, and throughout the whole protoplasm are numerous vacuoles 

 which appear and disappear, shifting about rapidly (Fig. 7, h). At the same time 

 with the beginning of this stage, there is a very sudden decrease of turgidity in the 

 sporangium, which is shown by the flattening of the terminal wall of the apical 

 papilla, previously convex outwa'"d, and by a complete change in position of the basal 

 wall (Fig. 7, h). This wall has been luitil now, as before stated, convex downward, 

 on account of the greater turgidity of the sporangium than of the lower part of its 

 hypha. These relations evidently now become reversed, for the wall suddenly 



