796 Schwartz.—The Life-history and Cytology of 
ductive stage. This intervening stage, in which we get the disappearance 
and reformation of the nuclei, is known as the akaryote or chromidial stage, 
and is to be seen in PI. LXI, Figs. 11 and 12. The nuclei of the reproductive 
stage next undergo typical karyokinetic mitoses, as shown in Fig. 13. I 
have not been successful in finding any reduction nuclear division, there 
not being any noticeable difference in the size of the spindles. In all 
probability, however, meiosis takes place, as has been observed by 
myself and others in various members of the Plasmodiophoraceae. At 
the close of these nuclear divisions the nuclei are considerably reduced in 
size ; unlike the vegetative nucleus, the chromatin is not collected into 
a central karyosome, but is found round the periphery of the nucleus, the 
centre of which is often clear. Cleavage occurs in the protoplasm, and 
a number of small independent uninucleate amoebae are formed. These 
amoebulae are crowded together, sometimes in spherical or ellipsoidal 
masses. After the secretion of a cell-wall by each amoebula a spore is 
formed, and the masses of amoebulae are converted into the collections of 
spores or sorospheres. These spore masses may completely fill the cell or 
they may be comparatively small; they are usually hollow and enclosed by 
a common membrane. The akaryote stage is shown in Figs. 11 and 12, 
and various forms of spore masses are to be seen in Figs. 14 and 20. I have 
observed no conjugation of nuclei such as has been described by Prowazek 
in Plasmodiophora and Osborn in Spongospora , although I have carefully 
searched for it. The reduction in size of the spindles in the two reproductive 
mitoses prior to spore formation has been observed by myself in both 
5 . Veroniccie and X. Jtmci , and doubtless points to a corresponding karyo- 
gamy such as has been described by Osborn. The spores vary considerably 
in size, and have an average diameter of about 6 /x. 
Affinities of S. Graminis. It is obvious that X. Graminis is very 
closely allied to S. fund, the main points of difference being the greater 
rarity of the true sorosphere (spherical in shape) and the more amoeboid 
form of the organism. The affinities of the Plasmodiophoraceae with 
other Fungi I have discussed in my paper on X. Junci ; they differ from 
the non-parasitic Mycetozoa by their distinctive form of vegetative nuclear 
division, which has not been observed in the latter, in which also the 
akaryote stage is absent. 
Attempts were made to infect plants of Poet Annua by planting them 
in pots of soil infected with X. Junci , in which also some diseased Junci 
were planted. The Poa plants, however, kept quite healthy, thus showing 
the two organisms, X. Junci and 5 . Graminis , to be distinct. 
