ZOOLOaY AXD BOTANY, MICROSCOPYj ETC. 687 



New Form of Potato Disease.* — A hitlierto unknown form of the 

 potato disease, wliicli has been making slow but steady progress near 

 Stavanger during the last ten or twelve years, has recently begun to 

 show increased energy. The stalk of the plant is the part affected, 

 and here Herr Anda has discovered small white fungoid growths, 

 which after a time assume a greenish, and finally a black, colour, after 

 attaining the size of a small bean. While the fungus is rapidly in- 

 creasiag at the expense of the plant, the interior of the stem is first 

 reduced to a pulpy condition, and next shrivelled and hollowed out, 

 until nothing remains but a mere outer shell, which breaks down on 

 being touched. When the ripe black germs of the fungus have re- 

 mained in the earth through the winter, they are found after the 

 return of the next year's warmth to have developed small stalked 

 fruits filled with minute spores, which penetrate into the young plants 

 before they appear above the ground. The end of July or beginning 

 of August is the time when the ravages of the fungus are most con- 

 spicuous, and at those periods whole fields of potato plants are often 

 rapidly reduced to the condition of withered straw. 



Spermamcebse of the Saprolegnieae.f — As the result of a fresh 

 series of observations, N. Pringsheim confirms his previous statement 

 that the fertilization of AcMya and Saprolegnia is effected by means 

 of peculiar bodies, "■ spermamoebfe," which enter the oogonia ; in oppo- 

 sition to the view of Zopf,? that these bodies are nothing but parasitic 

 amoebae. 



He afBrms that the spermamoebfe are produced within the antheri- 

 dium, and do not occur in any other part of the plant ; that they are 

 formed only during the period of fertilization, and do not continue 

 any longer than the fertilizing tube. Parasitic amoebas endowed with 

 a power of motion he has never seen in the fertilizing tubes or oogonia 

 of the Saprolegnieee. It is impossible to confound the spermamoebse 

 with the well-known swarmspores of Chytridie^ — Olpidiopsis, Woro- 

 nina, Bozella, and a BJiizidium-hke parasite — which enter healthy 

 Saprolegnieee by boring through the walls of the fertilizing tubes. 

 The anaoebae which abound in the water surrounding the Saprolegniere 

 never enter the tubes in this way. 



The bodies which Zopf describes as larger and smaller amoebae, 

 Pringsheim believes to be structures of a peculiar nature, which super- 

 ficial observation might mistake for the spermamoeb». But they are 

 distinguished from them by a variety of characters, morphological, 

 optical, and chemical. They are grains of a kind of fungus-cellulose 

 or of some modification of it. These occur abundantly in the ferti- 

 lizing tubes, and some of them pass into the oogonia among the 

 oospores. 



Pringsheim further supports his view as to the mode in which the 

 process of fecimdation is effected in the Saprolegnieae — which differs 

 also somewhat from that of de Bary — by the following considera- 



* Naturen, 1883. Cf. Nature, xxviii. (1883) p. 281. 



t Bot. Centralbl., siv. (1883) pp. 378-82 ; also Pringsheim's Jahrb. Wiss. Bot., 

 xiv. (1883) pp. 111-31. Of. thi3 Journal, supra, p. 676. 

 X See this Journal, ante, p. 248. 



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