240 COLOCASIA bLIGHt. 



during the second active stage. In some genera of Chytridiacew 

 the same purpose is apparently served by a period of quiescence of 

 the spore, during which the cilia are retracted to be again pro- 

 truded after a time sufficient to allow of a certain amount of passive 

 dissemination 1 . Sawada has also observed the formation of a second- 

 ary spore germinating by a hypha on the germ-tube of the primary 

 spore, but the formation of secondary zoospores has not been observed 

 either by him or by us and is certainly of infrequent occurrence. 



Sometimes the zoospores fail to escape, one or more being 

 left in the sporangium. After a time these cease to move, secrete 

 a wall and germinate in the usual manner. The germ-tube appears 

 to be unable to pierce the sporangial wall and can only emerge 

 through the opening (PI. Ill, Fig. 11). 



Recently matured sporangia germinate for the most part by 

 giving zoospores, when placed in fresh water. Frequently, however, 

 a certain number fail to form zoospores but germinate directly by 

 a hypha. In sporangia, from their natural habitat on the leaf, 

 the germ-tube arises from the papilla, giving a stout branching 

 hypha, which may form a mycelium or give secondary sporangia 

 after a short growth. This type of germination will be more fully 

 described (from cultures) below. 



Some observations were made on the formation and discharge 

 of the zoospores. The ripe sporangium contains a single vacuole 

 of variable size. This is at first irregular and changes shape with 

 the slow movements of the intersporangial protoplasm ; then it 

 becomes spherical and ultimately disappears suddenly. The pro- 

 toplasm itself is at first coarsely granular and with a tendency to 

 form clumps. Later on it becomes more finely granular and after 

 the discharge of the vacuole it is almost homogeneous. About 

 five minutes after the vacuole disappears, the first cleavage lines 

 of the spore-origins become visible and the protoplasm contracts 

 slightly so as to leave a clear space just inside the wall. Soon 

 after, discharge occurs, in the manner so often described for Phytqph- 



1 Butler, E. J. he. cil., p. 121 and, Barrett, J. T. Development and Sexuality of some 

 species of Oljridiopsis, Ann. of Bot., XXVI, 1912, p. 215. 



