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STATE HORTICULTURAL SOCIETY. 



Like all Cercosporce the vegetive threads of the fungus usually grow 

 largely in the interior of the leaf and when the nutriment at the affected 



spot is nearly exhausted, clusters of fruiting threads 

 arise from the vegetive ones, and issuing from a 

 stoma of the leaf bear elongated spores at their ends. 

 Two clusters of the fruiting threads of Cercospora 

 Apii are shown at a and h in figure 5, while c rep- 

 resents a single fruiting thread with a spore still 

 attached, and free spores are shown at d and e. 



The fungus was first described by Fresenius. The 

 description given by Saccardo represents the form 

 developed under normal conditions, the hyphae 

 measuring 40 — 60x4 — 5 and the spores, or conidia, 

 50 — 80x4. The form of the conidia is given as 

 obclavate, i. e., the base or end at the point of attach- 

 ment with the hyphae is greater in diameter than the 

 distal extremity. The conidium in situ at the end of 

 the hypha, figure 5, c, shows this character well. It 

 was also observed in numerous other cases. Further- 

 more the free or abjoiuted conidia nearly always pre- 

 sent a well defined scar at the larger end as shown in 

 d and e, figure 5. This scar indicates the place of 

 attachment to the hypha, the corresponding scar on 

 the hypha being at the end or at one of the genicu- 

 lations as shown in a and h, figure 5. The explana- 

 tion of several scars appearing on a single hypha is 

 that after a conidium is abjointed from the end, the 

 hypha then grows out at one side of the scar and 

 bears another conidium at the end, and so on. These 

 scars at the base of the conidia enable one to deter- 

 mine their form even when they are not attached to 

 their parent hyphae. 



In the report of the mycological section for 188G is a short note on the 

 distribution of this fungus in the United States. The form of the conidia 

 is not given in the text, but they seem to be inverted in the illustration 

 where they are shown to be attached by their small ends to the hyphae. 

 Figuring them thus is equivalent to calling them clavate with reference to 

 their relation to the hyphae which is contrary to the original descriptions 

 and also to fact. 



In the report of the New Jersey station for 1891 (1. c. ) the conidia are 

 described as club-shaped. No figure is given and we infer that the writer 

 used the term "club-shaped" without any reference to their relation to the 

 hyphae. 



Under normal conditions the fungus is confined to well defined spots 

 on the leaf with an irregular, slightly raised border. During excessively 

 wet weather, as the leaf tissue is dying, it may spread to portions of the 

 leaf where the spots are not so well defined. Such conditions also induce 

 a much longer growth of the tufts of hyphie and their conidia. Figure 5 

 a and d represent such forms in comparison with h and e developed under 

 normal conditions. The measurements including such variations are as 

 follows: Hyphae 50 — 150x4 — 5; conidia 50—280x4 — 5. The figures* are all 



_*A11 the figures where the scale is shown are drawn with the same combination, the objects being mag- 

 nified 30 times more than the scale. 



