THE FORMATION OF HYPHAL FUSIONS 



13 



spinosa, and Sporodinia grandis, according to Burgeff, 1 in a single 

 mycelium some branches become (-f) and others ( — ) in sex, and 

 conjugation occurs only between a (+) hypha and a ( — ) hyplia 



Si 



arasi 



Flo. 5. — Diagram showing in one plane stages in the union of Parasitella sim- 

 plex with one of its host Mucorineae (Absidia glauca, Rhizopus nigricans, 

 etc.). a, a hypha of Parasitella has grown toward, and has applied its tip 

 to, the side of a relatively thick host-hypha. The nuclei of the parasite 

 are shaded, and those of the host left clear. Nuclei are collecting at the 

 end of the Parasitella hypha. b, a septum has been formed near the end 

 of the Parasitella hypha ; the cell so formed contains about ten Parasitella 

 nuclei. These nuclei are enlarging, and the Parasitella cell is about to 

 fuse with the host-hypha. c, the Parasitella cell has now fused with the 

 host-hypha and is enlarging, while the adjacent part of the Parasitella 

 hypha is also enlarging as a preliminary stage in the formation of a spore. 

 d, the Parasitella cell (Schropfkopfzelle = cupping cell) is sending out 

 lateral processes, its own nuclei have diminished in size, and host-nuclei 

 are wandering into it, while the future spore is still enlarging, e, the 

 Parasitella cell has now sent out a number of radiating processes which 

 partially envelop the spore. The cell with its processes constitutes a gall 

 (the Schropfkopf ). The gall-branches contain Parasitella nuclei at their 

 ends and host-nuclei in their middle and basal parts. One of the gall- 

 branches is becoming secondarily infected by a Parasitella hypha at s. inf. 

 The Parasitella spore, known as a sicyospore, is now fully developed ; it is 

 cut off from the hypha which bears it by a septum, its wall is thickened 

 and covered with calcium-oxalate crystals, and it contains numerous nuclei 

 and many oil-drops. From Burgeff's Untersuchungen fiber Sexualitat und 

 Parasitismus bei Mucorineen. 



(Fig. 4). He also holds that under certain conditions a (-J-) hypha 

 can change into a ( — ) hypha, and vice versa. 



Burgeff 2 described in detail the relations between the parasites 



1 H. Burgeff, Joe. cit., pp. 32 43. 



Ibid., pp. 91-135. 



