402 REPORT OF THE HARVARD AFRICAN EXPEDITION 
it could not be recovered from the culture which though previously sealed had 
become contaminated and overgrown with bacteria. Sections of many of the 
diseased plants, roots, stalk, and pieces of the leaves, were preserved in formalin 
and in Zenker’s solution in Africa and sectioned after our return to this country. 
They have been stained by safranine, haematoxylin and eosin, Giemsa’s solution, 
and Levaditi’s stain. A histological study of sections of the tissues of the 
diseased plants does not reveal as large a number of bacillary bodies as we 
observed in fresh, unstained preparations. However, they are present in small 
numbers, staining, and decolorizing by Gram like delicate bacilli or rickettsia. 
In the sections of several of the diseased plants, larger rounded bodies are also 
present which are evidently the spores of fungi. While usually they are circular 
in outline, measuring from 2.44 to 4.5u in diameter, occasionally a dividing form 
roughly dumb-bell in shape is seen. The stem of two of the plants is richly 
infected with the fungus and one or two of the micro-organisms are present in 
many of the cells. Occasionally there is a group of them within a single cell. 
They, however, have not yet been found in the cells of the terminal leaves. In 
addition to these conditions, one finds in some areas that the cytoplasm of the 
cells is vacuolated, in others that the chloroblasts in large areas show distinct 
loss of pigment. No protozoa have been discovered in the sections. 
Kunkel,! Goldstein,? Rawlins and Johnson,’ Smith * and Hoggan *® have all 
reported intracellular bodies said to resemble more or less the Negri bodies of 
rabies, or the Guarnieri bodies of variola in corn, tobacco, sugar cane, Chinese 
cabbage, and Hippeastrum mosaic. It has been suggested that these intracellu- 
lar bodies might have some etiological significance. Nothing suggesting Negri 
bodies could be found in the sections of our African mandioca. The recent work 
of Holmes ° with excellent photomicrographs seems to support the idea that these 
intracellular bodies which have been found in mosaic are not of a parasitic nature, 
since no definite nucleus can be demonstrated in them. Some of his photomicro- 
eraphs show dot-like and apparently short bacillary forms of chrondriosomes 
in the intracellular bodies, and Holmes considers this to be evidence for the view 
that the intracellular body in Hippeastrum mosaic consists of living cytoplasm. 
In addition to these intensely staining bodies he also found spheres containing 
deep-staining peripheral single or, rarely, double balls. These spheres were very 
definitely formed and easy to recognize. They were found in the cell cytoplasm 
in diseased plants but not in that of healthy plants. He further remarks that 
whether the intracellular body represents a stage of a foreign organism, a mass 
of plant cell cytoplasm containing virus, or a mass of plant cell cytoplasm not im- 
mediately in contact with the virus but stimulated by the disease condition is 
not known. Elsewhere he points out that the dot and short bacillary forms could 
not be distinguished by Giemsa’s stain, although they took other dyes intensively. 
1 Kunkel: Science (1922), LV, 73. 
2 Goldstein: Bull. Torr. Bot. (1924), LI, 261. 
3 Rawlins and Johnson: Amer. Jour. Bot. (1925), XIT, 19. 
4 Smith: Ann. Mo. Bot. Garden (1926), XIII, 425. 
5 Hoggan: Jour. Agr. Research (1927), XX XV, 651. 
6 Holmes: Bot. Gaz. (1928), LXXXVI, 50. 
