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W. R. IVIMey Cook,
on germination gives rise to swarm spores which fuse in pairs to produce a fresh plasmodium. The species causes hypertrophy of the host tissue and mumours are produced,
Two species are recognised, $. Callitrichis has been found in Scandinavia and Russia, while S. radicicolus has been recently found in South Africa. From such a scattered distribution it seems likely that further species belonging to this genus will eventually be found.
I. S. Callitrichis Lagerh. & Winge. (Pl. 15, fig. 1).
Winge, O. Arch. f. Bot. Vol. 12. Pp. 1–39. 1912.
Spore-cakes composed of two layers of spores closely appressed to one another, 20-30μ in width, composed of up to two hundred spores. Spore measures 6μ—74 long by 4-5 in diameter, Spores on germina- tion give rise to swarm spores from which eventually plasmodia are produced. The organism has been recorded from Norway in Callitriche vernalis, and in Sweden and Russia in C. autumnalis.
2.
S. radicicolus Cook. (Pl. 15, Fig. 2).
1931.
Cook, W. R. Ivimey, Annales Mycol. Vol. 29. Pp. 313-324.
Spore-cakes smaller than in last species, 10μ-12 in width, each spore-cake containing about fifty spores. Spores measure 3.8-4.2 in diameter. On germination they give rise to swarm spores which fuse in pairs and infect fresh cells of the same tumour. Plasmodia are restricted to the walls of the host cells but not to the same extent as in the last species. The organism attacks the roots of Gynandropsis pentaphylla, and has only been found in the country near Pretoria, South Africa.
In both these species the difference between the spore-balls of Sorosphæra and the spore-cakes of Sorodiscus is clearly seen, and the absence of any appreciable cavity between the two layers of spores is one of the most important characters by which the two genera can be distinguished. In addition the tendency for the plasmodia to become contiguous with the walls of the host cells is also a distinguishing character.
Gerus 4. Spongospora Brunchorst.
Brunchorst, J. Bergens Museums Aarsberstnung. 1886, Pp. 219-226.
1887.
Spores spherical with smooth thin walls; aggregrated together into irregular shaped masses with hollow spaces, On germination spores give rise to swarm spores which conjugate in pairs to produce fresh plasmodia. These finally become converted into spore-balls which are not enclosed in ? common membrane. The genus is distinguished by the arrangement of the spores in sponge-like masses. These really consist of more or less spherical aggregations of spores lightly joined together, but here and there separated by irregular furrows running through the spore-ball. No mem- brane has been observed around this structure.
The Hong Kong Naturalist.
The Hong Kong Naturalist Supplement,
No. 1.
Plate 16, figure 1.
Spangospora subterranca, Spores x 320.
Plate 16. figure 2.
Spongospora cumpanulae. Spores x 320.
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