188 BOTANY 



More recently Sheffield has confirmed the various observations 

 recorded above in different species of (Enothera, and finds like 

 these different authors that there is transference of chromatin 

 from the nucleolus to the developing spireme. 



It will be seen, that contrarv to the view of the older workers, 

 the nucleolus apparently plays an important part in the activities 

 of the nucleus, and is not a reservoir of waste material as was 

 thought at one time. But although the examples cited above do 

 show that a significant relationship exists between the nucleolar 

 material and the cyclic alterations of the chromosomes, the exact 

 nature of this relationship yet remains to be determined. 



NUCLEAR DIVISION 



It is not proposed to deal here with the ordinary process of 

 mitosis in the nuclei of the higher plants. This aspect of nuclear 

 division is dealt with at length in the ordinary text-books on the 

 subject, and only certain peculiar methods of nuclear division 

 found in some of the lower fungi, algse and the bacteria will be 

 discussed. 



Plasmodiophorales. The members of this order of fungi form 

 a natural but very isolated group, with no evident affinities to the 

 rest of the fungi. They exhibit two types of nuclear division in 

 the course of their life-history, one during the growth of the 

 amoeba, which is continued up to the time of spore formation, and 

 the second represented by two successive divisions directly 

 associated with reproduction. The first method of nuclear 

 division is often termed " protomitosis " or " cruciform " division, 

 while the method of division associated with spore formation is 

 typically mitotic and apparently constitutes a meiotic phase. 

 Separating these two different types of division is the so-called 

 " akaryote " stage, during which stainable chromatin is extruded 

 into the cytoplasm. 



Cook has investigated Ligniera junci in regard to its nuclear 

 divisions. This member of the Plasmodiophorales is a root 

 parasite of Callitriche stagnalis. The resting nucleus is about 

 2-5 jx in diameter, more or less spherical in shape and surrounded 

 by a deeply staining nuclear membrane. The chromatin forms a 



