REPORT OF COMMITTEE ON PUBLICATION 141 



at this time by the pulling apart of the spores. There is a considerable jerk- 

 ing and wrenching before they separate. At times two spores remain 

 attached for a long time and finally, by dint of much pulling, they snap apart 

 and swim away. At other times as many as four or five spores are appar- 

 ently joined together by their flagella. Thus it would seem that the flagella 

 are slender threads of protoplasm puled from the spores as they split apart." 

 Clinton (1906) has made a similar suggestion in the case of Phytophthora 

 phaseoli, videlicet, "The motion is due to a slender thread or a cilium drawn 

 out by the pulling apart of the narrow zone connecting two adjacent 

 bodies . . ." Istvanffi (1913.13) claims that the flagella are present on 

 the spores before they emerge from the conidium and infers that there is 

 no hesitation after emergence. He does not, however, figure them in this 

 way. We have never seen the flagella on the newly formed zoospores in the 

 conidium before evacuation though they were very clearly stained on those 

 which were free and upon mature zoospores which were unable to escape 

 from the conidium (vide post). Hence it is the writer's opinion that the 

 flageUa are produced during the period of emergence or while the zoospores 

 are hesitating at the apex. The method of staining with methylene blue 

 and carbol-fuchsin, has also revealed the fact that the spores are not con- 

 nected by their flagella but by other minute strands of protoplasm (PI. Ill, 

 fig. 7). 



"Sometimes all of the swarmspores do not escape from the conidium at 

 once, but one or two remain swimming about within. These spores experi- 

 ence considerable difficulty, so to speak, in escaping, seeming to be unable 

 to squeeze their nuclei through the opening. If they do manage to escape 

 they are usually constricted at the center into a dumbbell shape. 



"The number of zoospores produced varies greatly. The large conidia 

 may produce as many as fifteen to seventeen while some small ones have 

 only one or two. The normal number is five to eight." 



"The conidia containing the oil drop germinate readily at times. In this 

 case the oil drop is left behind in the conidium, the entire mass of proto- 

 plasm going to make up the swarmspores." 



"The shape of the swarmspores is plano-convex with a keel or ridge 

 along the flat side. In the center near the flat surface there is a light 

 hyaline spot, the nucleus. Near it, and less brilliant, is another spot which 

 by tinting with stains appears to be a vacuole. From two points on each side 

 of the nucleus arise the flagella, which are of unequal length (PI. Ill, fig. 6)." 

 Certain of the European investigators, Viala (1903) and more recently, Ravaz 

 and Verge (1913), have stated that the flagella are terminated with a small 

 lobe. According to the writer's observations this lobe is never present but 

 at times the end of the flagellum may form a small loop which gives such an 

 impression. In this connection, Istvanffi says ". . . Treated according to 

 the methods of Zettnow, one may see that the ends of the cilia are not lobed 

 as they are most often represented, their length is about 15 to 20/t." 



"This is the normal shape of the spores but there are many exceptional 

 shapes produced at times. It is quite apparent that when the spores are 

 newly formed and escaping from the conidium, they are very plastic and 

 capable of taking any form, but once they are fixed in any given shape it 

 is difficult for them to change. Thus, if in pulling apart the spore becomes 

 pyriform or some irregular shape it remains so. 



