334 



Edwin F. Hopkins 



are shown in figures 36 and 37. 3 Usually young conidiophores were chosen 

 for study because of the firmer attachment of the conidia. The prepa- 

 ration of the mounts required considerable patience because of the delicate 

 attachment of the conidia, and oftentimes many mounts were prepared 

 before one was obtained which showed clearly the details of structure. 

 When young, the conidia are hyaline, but as they mature they assume, 

 in mass, a brownish color. Microscopical examination shows that most 



of this color is in the spore 

 wall. The conidia are obo- 

 vate, and when shed, the 

 short sterigmata may some- 

 times be seen still attached 

 to the spores. 



The conidia vary con- 

 siderably in length and to a 

 less extent in width, but 

 this variation does not de- 

 part greatly from a mean 

 which is more or less con- 

 stant. This is shown graphic- 

 ally in figure 38, which 

 represents the measure- 

 ments of one hundred spores. 

 One curve expresses the vari- 

 ation of the spore length 

 and the other that of the 

 spore width. 



The spores measured were from single-spore cultures and developed on 

 sterilized tulip leaves in petri dishes. Abundant conidial fructifications 

 were formed which were practically identical in appearance with those 

 occurring in nature. They were mounted in the mounting fluid previously 

 described 3 and were measured under the oil-immersion lens by 



Fig. 36. development of conidia of botrytis 

 tulipae. x 600 



Illustrating the bud-like manner of their formation. 

 (Camera-lucida drawing) 



3 In studying the detail of the conidiophore, especially the attachment of the conidia, satisfactory mounts 

 were obtained by first adding to the material on the slide a drop of 70-per-cent alcohol in order to "wet" 

 the conidiophores rapidly. The material was then flooded immediately with a mounting fluid prepared 

 by mixing equal parts of 2-per-cent potassium acetate in water and 40-per-cent glycerin in alcohol and 

 then adding a trace of copper acetate. The excess mounting fluid was removed with filter paper and the 

 mount covered with a cover glass. Such mounts keep very well, do not dry out, and may be kept per- 

 manently when ringed with balsam or gold size. 



