Osborn , — Spongospora subterranea , ( WallrotZi ) Johnson. 329 
were stained with Flemming’s triple stain, gentian violet and orange, or 
Heidenhain’s iron haematoxylin. As counterstains with the last-named, 
orange G, erythrosin, or light green ( Lichtgriin ) dissolved in clove oil were 
tried, also one per cent, aqueous Congo red. In spite of its poor keeping 
qualities, light green was found to be the most generally useful, as It clearly 
differentiated the host protoplasm from that of the parasite. 
Summary of Present Knowledge. 
Briefly stated, our present knowledge of Spongospora is as follows. 
Uninucleate myxamoebae are observed in young potato cells, 1 though this is 
disputed by Johnson. 2 These subsequently fuse to form a plasmodium, 
while it is stated that fresh cells are invaded by a passage being bored 
through their walls. 3 At the approach of spore formation the plasmodium 
becomes very vacuolar, and then, according to Massee, a hollow sphere is 
formed, in the walls of which lacunae appear, while later polygonal cells 
(spores) are cut off, arranged in a single layer. Johnson 4 has corrected 
this statement, pointing out that the spore mass is a f sponge-like ’ body. He 
further states 5 that each spore contains a number of nuclei (4 or 8), com- 
paring this with Jahn’s G and Olive’s 7 observations on Ceratiomyxa. Massee 
saw only a single amoeba, which escaped on the germination of the spore. 
Life-history. 
Vegetative phase. Actual infection of the potato tuber by Spongo- 
spora has not been seen, nor have infection experiments been successful.- The 
earliest stage in the life-history that has been observed is that of a single 
uninucleate amoeba in a young potato cell near an eye (PI. XXVII, Fig. 1). 
The amoeba is somewhat rounded in outline, and consists of finely granular 
protoplasm, which has different staining properties from that of the host cell, 
so that it can be clearly differentiated from it. The nucleus appears to con- 
form to the well-known Mycetozoon type, described by Lister 8 and others. 
It has a membrane and linin network bearing chromatin granules, as 
well as a deeply staining body occupying a central position (Fig. 17). This 
central body retains the safranin with triple stain, and acquires an intense 
black with iron haematoxylin. As at times it appears to contain all the 
chromatin of the nucleus, it is, perhaps, best referred to as the karyosome, 
rather than as the nucleolus. 
The nucleus divides in a manner to be described later, and this is 
generally followed in the early stages of infection by a division of the amoeba 
1 Massee, G. : loc. cit., p. 596. 2 Johnson, T. : loc. cit., 1909, p. 171. 
3 Massee, G. : loc. cit., p. 597. * Johnson, T. : loc. cit., 1908, p. 455. 
5 loc. cit., p. 456. 6 Jahn, E. : Ber. d. deutsch. bot. Gesell., vol. xxvi a, 1908. 
7 Olive, E. W. : Trans. Wiscon. Acad. Arts. Sci. Litt, vol. xv, pt. ii, 1907, p. 753, 
8 Lister, A. : Journal Linn. Soc. Bot., vol. xxix, 1893, p. 529. 
