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®b5crvation6 on tbc Structure of 

 C^etopus CauM^ue/' 



IN the following paper a short account is given of the structure 

 of the vegetative and reproductive organs of Cystopus candi- 

 dus, a fungus parasitic on cruciferous plants, and especially 

 abundant on the common Shepherd's-purse {Capselia bursa-pas- 

 ioris), on which it forms shining white patches, often of consider- 

 able extent, on the stems, leaves, and fruits. 



The mycelium consists of non-septate hyphae, which ramify 

 in all directions between the cells of the host plant, and often 

 produce extensive hypertrophy of the organ attacked. Here and 

 there small spherical haustoria are developed oil the hyphae, and 

 these penetrate directly into the cell cavities. Both hyphae and 

 haustoria contain a granular protoplasm, in which numerous nuclei 

 can be seen. The structure of these nuclei can be made out by 

 careful staining and examination under a sufficiently high power, 

 as was shown by Fisch. Each nucleus is vesicular, and contains 

 a large nucleolus, which stains deeply, and is surrounded by a less 

 deeply stained substance, in which some indications of a granular 

 or thread-like structure may at times be observed. 



The reproductive organs are of two kinds, asexual and sexual. 

 The asexual organs are formed just beneath the epidermis of the 

 host-plant ; they are club-shaped branches of the mycelium, from 

 which zoosporangia are cut off by constriction and formation of a 

 double wall at the apex. These branches contain granular proto- 

 plasm derived from the mycelium, and numerous vacuoles. A 

 few nuclei are found scattered in the protoplasm, the number 

 being variable, from five to twelve. The structure of the nucleus is 

 similar to that in the mycelium, but is more easily made evident. 



In the formation of the sporangium a part of the protoplasm 

 accumulates at the apex, together with a few nuclei, four or five, 

 or perhaps more ; this is then separated from the club-shaped 

 branch by constriction of the cell-membrane. A double cell-wall 

 is then formed which completely cuts off the sporangium from the 



* Extracted from a paper by Harold T. Wager in the Report of the 

 British Association, by G. H. Bryan. 



