DAMPING OFF. 259 



pendicular to this prostrate one. As the new one increased in 

 height the old one gradually lost the protoplasm both from the 

 forming sporangium and the stalk. In the course of 4 to 5 hours 

 the sporangium was mature and the conidium ejected, when the 

 sporangium and stalk collapsed and remained as a flabby mem- 

 brane attached to the wall of the old stalk and sporangium which 

 was still in the water and which still remained intact. 



The conidium is capable of germinating immediately when 

 there is sufficient moisture and the behavior seems to be mani- 

 fested in three different ways according to the amount of moisture, 

 or in some cases perhaps according to the proximity of the host. 

 If the spore is entirely immersed in water a long slender germ 

 tube is put forth similar to the tube which is emitted from the 

 terminal cells of the botryose body of a vegetatively mature plant. 

 Where less water is present the conidium germinates by develop- 

 ing a germinal vesicle, or proembryo as described above. 



From the inner face, the one lying next the prothallium cell, 

 of the broader end of the proembryo, a minute tube is thrust out 

 which pierces the cell wall of the host and grows out to the cen- 

 ter of the cell lumen where in the ordinary way it enlarges into 

 the first ovoid body of the new plant (fig's. 38, 40). In other 

 cases probably, where there is still a less quantity of moisture, 

 the tube from the germinating spore is directed upward or away 

 from the host and becomes a sporangium with a very short stalk 

 or only the short narrowed end of the sporangium which serves 

 as a stalk. Before this conidium is ejected from this secondary 

 sporangium if it be immersed in water, the protoplasm will grow 

 out into a long slender germ tube. If it were only partially 

 immersed it might as in the case of the primary sporangium noted 

 develop a new sporangium. In the case of the primary sporan- 

 gium which was immersed in water and which developed a new 

 sporangium at the base of the old one, as described above, the 

 base of the stalk was not entirely immersed. 



As stated above the primary sporangia in the cases observed 

 developed from some of the larger of the external cells of the 

 cluster. In one case this took place while the inner cells 

 were developing resting spores (fig. 34). It may be possible that 

 the sporangia are always developed from somewhat larger and 

 richer cells of the periphery but more likely others of the cells can 



