WIXGE, CYTOLOG. STUDIES IX THE PLASMODIOPHORACE.^. 13 



has the form of a plate — as was also later stated by Blom- 

 EiELD and Schwartz — though the most chromophilous parts 

 are lying in the periphery of the plate as rather conspicuous 

 grains. The number of these is probably constant, but very 

 difficult to determine on account of their smallness and the 

 surrounding chromophilous substance. In several cases I have 

 observed that their number is not very great. 



During the first part of the sporogonic phase the nucle- 

 olus disappears totally (fig. 66 and 67), which according to 

 the description and illustration by Maire and Tisox occurs 

 owing to the nucleolus (the caryosome) growing smaller and 

 smaller, and at last becoming pulverised into granula, when 

 a new nucleolus appears afterwards, which immediately by 

 the first of the two mitotical divisions again disappears. 

 This new nucleolus I never saw nor any stage, at which the 

 nuclei are perfectly devoid of chromatical contents. When 

 Maire and Tisox says that for some time the nuclei are 

 seen only as weak lightnings in the plasma, I suppose that 

 it is average-cuts through a myx-amoeba — cuts, in which 

 only a part of the cavity of the nuclei is shown, not the 

 chromatical parts — which have given it such an appearence. 

 Several times I myself have got preparations of apparently 

 empty cavities of nuclei, but as far as I can make out it is 

 always, as mentioned above, a gleam-cut through a great 

 number of nuclei, — and that such cuts are possible may be 

 explained in this way that the nuclei very often are situated 

 on one level along the cell-wall of the host. 



Strange to say Blomfield and Schwartz (1. c.) have 

 noticed the same total disappearance of the nuclei and the 

 same lightnings in the plasma and declare (p. 30) that »it 

 seems to us to be incertain whether the vacuoles seen at 

 this stage are the remains of the vegetative nuclei or whether 

 they are freshly produced in the plasma. »^ — On the con- 

 trary they do not mention the appearance of any nucleolus 

 after the disappearance of the first one at the transitional 

 stage between the vegetative and sporogone phases, but are 

 of opinion that the nucleolus before disappearing becomes 

 »more irregular in shape and smaller in size», and that the 



^ In a later memoir: The Life-history and Cytology of Sorosphaera 

 Graminis (Annals of Botany, vol. XXV, 1911) Schwartz remarks about 

 the same vacuoles: »In these vacuoles apparently fresh nuclei are formed.» 



