646 
Ferdmandsen and Winge. — Ostenfeldiella , 
The Biology of the Fungus and the Anatomy of the 
INFECTED DlPLANTHERA STEM. 
As may be seen from Text-fig. 1, a long row of internodes is infected 
by the fungus, but the uppermost one is still fresh and living ; it is thus 
evident that the shoots continue to grow in length in spite of the presence 
of the parasite. It was therefore to be expected that the youngest stages 
of our fungus might be found in the top of the stem, for which we prepared 
some slides with longitudinal sections through the growing apex of a shoot. 
The sections were stained with safranin-anilin-blue-goldorange. Text-fig. 4 
shows a part of such a section, only the right side being entirely represented. 
Near the left side lies the central cylinder of the stem (a), and in the cortex 
to the right ( b and c) are seen the two tissues previously mentioned, viz. the 
inner and the outer cortex. The nuclei of the host plant are shaded. In 
some cells are seen very small circles, one or more in each cell, representing 
uninucleate amoebae of the parasite, and these occur also in the very top 
of the growing zone. In the meristematic parts of the stem one always 
finds these amoebae uninucleate, hence it becomes evident that the nuclear 
divisions of the parasite are always followed by division of the myxoplasm 
itself — a fact that seems to be very rare in the Plasmodiophoraceae, these 
organisms having commonly a tendency to become plurinucleate very soon 
after infection. 1 Further, we must suppose that this occurrence of a single 
or a few uninucleate amoebae in the cells of the meristematic tissues of the 
host plant must be due to the fact that the divisions of the parasite are 
keeping pace with those of the host cells. 
The uppermost embryonic internode, which is not yet deformed 
contains only uninucleate myxamoebae ; the next, slightly swollen, but yet 
light-coloured internode, has in the lower part already pluri- to many- 
nucleate myxoplasms ; while the sporogenous plasms and the spore-balls 
are, as a rule, found only in the third conspicuously swollen and brown- 
coloured internode (PI. XLV, Fig. 2). The succeeding internodes are 
completely filled with mature spore-balls (Text-fig. 4). 
As seen from Text-fig. 4 and PI. XLV, Fig. 4, the parasite only infects 
the inner cortex of the stem, 2 no myxamoebae being met with in the central 
cylinder nor in the cells of the outer cortex. The vascular bundles in the 
cortex seem always to be free from myxamoebae. The outer cortex, which, 
as stated, is free from the fungus, is filled with starch grains, these latter not 
being developed in the tissue attacked by the parasite (PI. XLV, Fig. 3). 
1 The same is stated for Sorosphaera Veronicae, Schroet., by R. Maire and A.Tison : La Cytologie 
des Plasmodiophoracees et la classe des Phytomyxinees (Ann. Myc., 1909). 
2 Also in the host plants of Sorosphaera Veronicae , Schroet., and Sorodiscus Callitrichis , Lagerh. 
et Winge, the epidermis and the outermost layers of the cortex are free from the parasite, the central 
cylinder however being sometimes infected. 0 . Winge : Cytological Studies in the Plasmodio- 
phoraceae. Archiv f. Botanik, vol. xii, no. 9, 1912, p. 18. 
