ZOOLOGY AND BOTANY, MICBOSCOPY, ETC. 805 



C. Lemnce. Inhabits the large intercellular spaces of the paren- 

 chyma of Lemna trisulca. Cells usually spherical or elliptical ; that 

 part of the germinating zygozoospore which remains outside the 

 epidermis becomes a spherical head of cellulose. 



EndospJicBra. Each cell breaks up by repeated bipartition into a 

 number of daughter-cells surrounded by a cell-wall, out of which the 

 spherical zoospores are formed by further bipartition. On escaping, 

 those from the same mother-cell conjugate, and, like those of 

 Chlorochytrium, penetrate the living tissue of the host. The zoospores 

 are formed only in the spring ; the new generation takes a full year to 

 mature. 



E. biennis. Inhabits the intercellular spaces of the subepidermal 

 parenchyma of leaves of Potamogeton lucens. Cells usually spherical ; 

 the part of the germinating zygozoospore which remains outside the 

 epidermis dies off quickly. 



Phyllobium. At the time of maturity the green protoplasm of 

 each cell is differentiated into cylindrical or spherical portions, 

 which become transformed into smaller ones, and coalesce to form 

 zoospores. These are of two sizes, macrozoospores and micro- 

 zoospores ; the resulting zygozoospores penetrate the stomata of the 

 living or dead leaves of flowering plants. Each cell takes a year to 

 mature. 



P. dimorplmm. Inhabits the leaves of LysimacMa nummularia, 

 Ajuga, CJilora, &g. The zygozoospores put out germinating filaments, 

 which grow in the vascular bundles of the leaf -veins into branched 

 green tubes ; the protoplasm of each of these tubes congregates into a 

 spherical or elongated resting-cell, which hibernates, giving rise to 

 sexual zoospores in the next summer. According to external circum- 

 stances the development of the germinating filament varies greatly ; 

 it may be quite rudimentary, when small resting-cells are formed 

 without any filaments, which give rise to non-sexual zoospores. 



Scotinosphcera. When mature the green protoplasm of each cell 

 is differentiated into cylindrical or spherical portions ; these coalesce, 

 with the elimination of a red granular substance, into a single 

 spherical mass of protoplasm ; this divides by repeated bipartition, 

 the granular substance being again absorbed, into zoospores, which are 

 non-sexual, and penetrate the dead tissue of the host. The course of 

 development occupies a year. 



S. paradoxa. Inhabits dead or dying tissues of Hypnum and of 

 Lemna trisulca. Cells usually spherical ; zoospores fusiform. 



MICROSCOPY, 

 o. Instruments, Accessories, &c. 



Beck's " Ideal " Microscope. — In this instrument (shown as a 

 monocular in Fig. 166) the stage is of very thin and stiff brass with 



