828 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Parasites of the Saprolegniese.* — A. Fischer has made a detailed 

 examination of the group of minute fungi parasitic on the Sapro- 

 legniege, which were at one time taken for the reproductive organs 

 of their hosts, the organisms themselves for antheridia, their zoo- 

 spores for spermatozoids. They comprise the three genera Olpidiopsis 

 Cornu, parasitic on Saprolegnia ferax, Bozella on S. dioica, and 

 Woronina on Actilya dioica. The mode of observing them adopted 

 was to cultivate the Saprolegnia, &c, on larvse of ephemerides, which 

 became completely covered with the fungus in twenty-four hours, 

 the parasite always attacking the latter after the course of a few 

 days. 



After a general description, applying to the whole group, of the 

 structure and movement of the zoospores, and the mode in which 

 the parasite penetrates the host, in extension of previous observations 

 on the same points, j the author proceeds to a separate description of 

 each genus. 



Olpidiopsis is distinguished by its nearly spherical or shortly 

 elliptical sporangia with smooth surface, which are found in swollen 

 and deformed Saprolegnia-sa.cs. In addition to the ordinary zoospores, 

 there occur also spined sporangia of the same size as the smooth 

 sporangia, which perform the function of resting spores in the cycle 

 of development of Olpidiopsis. The smooth spineless sporangia are 

 developed both from the spores of the spineless and from those of 

 the spined sporangia under favourable circumstances, a single 

 sporangium only springing from each spore. The view of Cornu and 

 others, that the spined sporangia are organs of a sexual nature, rests on 

 inaccurate observation. The number of species of Olpidiopsis is 

 probably much larger than has yet been described, the parasites of 

 Cosmarium and other desmids probably belonging to this genus. 



Bozella forms a number of closely packed sporangia in uninjured 

 Saprolegnia-£la,ments. The wall of its sporangium is inseparable 

 from that of its host. Like the last genus, it forms also spined 

 sporangia. Each spore which penetrates the host developes within 

 it a large number of sporangia, the spore appearing to lose its 

 individuality, and its protoplasm to become intimately mingled with 

 that of the host. The same is the case with the spores from the 

 spined resting sporangia. This applies to the section of the genus 

 described by Cornu, and which may be termed the septigena-group ; 

 in another section the spore-forming organs are solitary. 



Woronina is characterized by the formation of a sorus. The fila- 

 ment is divided by septa, and in each chamber is developed a sorus 

 consisting of a larger or smaller number of sporangia. Each spore of 

 the sporangial sorus gives birth again to a sorus, one generally spring- 

 ing from each spore. The author was not able to confirm the state- 

 ment of Cornu that this genus produces also resting spined sporangia ; 

 the resting condition appeared, on the other hand, to consist of the 

 accumulation into cysts of a large number of sori, forming what may 

 be termed " cystosores," bodies resembling in external appearance 



* Pringsheim's Jahrb. f. wiss. Bot., xiii. (1882) pp. 286-371 (3 pis.), 

 f See this Journal, i. (1881) p. 87. 



