Abstract
A CHYTBIDIUM WITH TRUE REPRODUCTION.—Botanists are indebted to Dr. L. Nowakowski for a memoir on Polyphagus cuglenæ, in which they will find recorded for the first time the whole life-history of one of the most interesting of the group of vegetable parasites known as Chytridia. First described in 1855 by Bail, who was a pupil at Breslau of the illustrious F. Cohn, this species has now had all the mysteries of its life cleared up by the researches of Nowakowski, studying at the same university and under the same master. The Euglenæ on which it is parasitic will be well known to microscopists as a group of flagellate Infusoria, at one time found as freely-swimming forms, and at another passing into a resting stage. It is at this period of their existence that the Polyphagus attacks them. The minute spores are furnished with four or more delicate filaments, which project from the body of the spores like rays. One or more of these soon comes into contact with a Euglena, bores through its integument, and penetrates into its protoplasmic contents; it now becomes a haustorium, increases in size, often sends off other filaments, which go on the search for other specimens of Euglenae; in the meanwhile the body of the spore grows apace, and, if its haustoria be only fairly successful in catching Euglenae, soon increases to considerable (microscopical) dimensions, and in course develops into a pro-sporangium. Next a little bladder-like projection is seen slowly forcing its way out from this latter, and at last becomes developed into a zoosporangium, from which in time issue the cloud of zoospores, and so after a well-known fashion the vegetative development of this parasite is carried on. The presence of a true reproduction is, however, the great fact in the memoir. Among the individuals of Polyphagus developing in the interspaces of the dead Euglenæ will be found two forms; one larger than the other, and generally spherical in shape, is the female plant; the other, small and more or less club-shaped, is the male plant. From the former there is a tube-like prolongation which passes into a haustorium; from the latter there are several haustoria; these remain thread-like if they encounter no Euglenæ, or enlarge when they do. These two unicellular plants then conjugate, but after a somewhat strange and novel manner. The protoplasmic contents of the female plant project through an opening in the cell wall, forming slowly an oval mass (gonosphere), with the which a haustorium from a neighbouring male plant, coming into contact, there is a co-mingling of the contents of the two plants, and thereby a zygospore is produced; sometimes these have a quite smooth covering, at other times they are rough, with minute prickles. After a little rest the zygospore develops a zoosporangium, from which issue swarm-spores, and the cycle is complete. As the result of these investigations, the author would place the Chytridia forms in the group of the Siphomycetes. It will be Observed that though the whole contents of two cells go to form the zygospore, yet that the difference in the size of these cells is very marked, and that the behaviour of the gynoeciel cell reminds one of what takes place in an oospore. (Cohn's Beiträge zur Biol. der Pflanzen, Bd. ii. Heft 2, 1876.)
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Biological Notes . Nature 15, 458–459 (1877). https://doi.org/10.1038/015458a0
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DOI: https://doi.org/10.1038/015458a0