Notes . 
271 
A PRELIMINARY NOTE ON THE LIFE-HISTORY AND CYTOLOGY 
OF SPONGOSPORA SUBTERRANEA, W ALLROTH. — Though the life-history 
of Spongospora subterranea , the organism producing the ‘ Powdery ’ or ‘ Corky Scab ' 
of the potato, has to some extent been described already, 1 no account of its cytology 
has yet appeared. 
The organism is first apparent in young potato cells just below the surface 
of the tuber, as a uninucleate amoeba. This increases in size, while its nucleus 
divides by a special method of amitosis, not unlike that described for Sorosphaera 2 
and Plasmodiophora . 3 The amoeba itself divides by fission, so that a late stage 
shows many multinucleate amoebae in a single host-cell. Fresh cells are infected, not 
by a passage being bored through their cell-walls, but by the passing of amoebae into the 
daughter cells in the meristematic tissue. On the conclusion of the vegetative phase 
a plasmodium is formed, and the nuclei undergo a reconstruction. The chromatin 
passes out into the protoplasm as chromidia (akaryote stage), while later new nuclei 
are formed, apparently on different sites from the old ones. These nuclei fuse 
in pairs, the fusion being followed by a condition suggestive of synapsis. Following 
this state the nuclei divide twice by karyokinesis, the first of these divisions being 
marked by a longer spindle than the second, while in the latter eight chromosomes 
can be counted. These mitoses probably correspond to heterotype and homotype 
divisions. During the karyokinesis the protoplasm of the plasmodium has developed 
numerous cleavages ; subsequent to the divisions it rounds itself off about the nuclei 
and forms spores. These are about 5 /x in diameter, uninucleate, and are united 
in irregularly spherical masses, characterized by depressions and fissures giving the 
structure a sponge-like appearance. 
The main conclusions reached as a result of these observations are that Spongo- 
spora should be united with Plasmodiophora , Sorosphaera , and Tetramyxa in the family 
Plasmodiophoraceae. 
The account of the karyogamy 4 in the cysts of Plasmodiophora is not sub- 
stantiated by more recent work, 5 while no nuclear fusion has as yet been observed in 
the life-history of Sorosphaera . In the latter organism synapsis and reduction divisions 
are recorded just prior to spore-formation, and it is not impossible that a nuclear fusion 
has been overlooked. 
The karyogamy described for Spongospora and the two subsequent mitoses 
present a striking resemblance to the occurrences in the plasmodia of Arcyria and 
Trichiap and serve to strengthen the relationship between Plasmodiophoraceae and 
the Mycetozoa. 
T. G. B. OSBORN. 
The Cryptogamic Research Laboratory, 
Manchester University, 
November 1910. 
1 Johnson, T. (’ 08 ): Economic Proc. Roy. Dublin Soc. , vol. i, p. 453. Massee, G. (’OS) : 
Journ. Board of Agric., vol. xv, p. 592. Johnson, T. (’ 09 ) : Sci. Proc. Roy. Dublin Soc., vol. xii 
(N.S.), p. 165. 
2 Maire, R., and Tison, A. (’ 09 ): Ann. Mycolog., vol. vii, p. 226. Bloomfield, J. E.,and 
Schwartz, E. J. (TO) : Ann. Bot., vol. xxiv, p. 35. Schwartz, E. J. (TO) : Ann. Bot., vol. xxiv, p. 51 1. 
1 Nawaschin, S. (’ 99 ) : Flora, vol. lxxxvi, p. 404. Prowazek, S. (* 05 ) : Arb. a. d. kaiserl. Gesund- 
heitsamte, vol. xxii, p. 396. 4 Prowazek, S. : 1 . c. 6 Maire, R., and Tison, A. : 1. c. 
6 Kranzlin, Helene (’ 08 ) : Archiv f. Protistenkunde, vol. ix, p. 170. 
