﻿

I 



MITOSIS OF THE PRIMARY NUCLEUS IN SYNCHY- 



TRIUM DECIPIENS. 



Frank Lincoln Stevens and Adeline Chapman Stevens. 



(with plates XVI AND XVIl) 



The fungus Syjichytriiun decipicns Farlow invades single cells 

 ^ of the hog peanut [Falcata comosa (L.) Kuntze) and there causes 

 proliferation of the tissue until the host cell is imbedded in a 

 gall of considerable size. The parasite is at first seen resting in 

 the cytoplasm of the host cell and occupying it conjointly with 

 the host nucleus of that cell. The parasite, growing more rapidly 

 than the host cell in the early stage of its enlargement, soon 

 comes to occupy the whole cell' space, while the host nucleus 

 slowly disappears. During further gall growth the parasitized 

 cell becomes many times larger than when attacked. The cyto- 

 plasm of the parasite increases pari passu, continuing to fill 

 completely the host cell. Increase in cytoplasm is accompanied 

 by a corresponding growth of the Synchytrium nucleus. It thus 

 happens that while the nucleus of the invading Synchytrium 

 was at first very small, it later reaches proportions vastly larger 

 than the nucleus of the host plant, larger even than the 

 notoriously large nuclei found elsewhere in the plant king- 

 dom. The maximum diameter of the embryo sac nuclti of flow- 

 ering plants ranges in the neighborhood of 20-30/i and that of 

 e vegetative nuclei from 5 to 9 ft. The nucleus of this unicel- 

 lular fungus parasite often attains a diameter of 35 /i, with a 

 nucleolus 1 1 ^u or more in diameter. 



The vegetative period of the parasite is characterized by 

 increase in size of both the fungus body and its nucleus. This 

 period may be said to end and the reproductive period to begin 

 with those processes which lead to separation of this mass of 

 cytoplasm into numerous portions which are by further division 

 to become swarm spores. The first step toward the separation 

 of the cytoplasmic body is the division of this primary nucleus. 



th 



1903] 



405 



