198 PHYTOPHTHOKA PARASITICA. 



generally by one and rarely by two germ-tubes (Plate IV, Figs. 8 

 to 25). The germination does not seem to be affected by light 

 or darkness. Two sets of experiments were carried out to see the 

 action of light on the germination of zoospores. A little bit of 

 mycelium from a pure culture was transferred to tap water. 

 Within ten minutes an army of zoospores was actively moving 

 about. They were transferred to twelve slides, half of which 

 were kept in a moist chamber exposed to ordinary day-light at 

 laboratory temperature, while the rest were kept in a moist 

 chamber in a dark cupboard at the same temperature. In two 

 hours all the spores had germinated equally well in both the sets. 



The germination of the sporangia takes place in three different 

 ways. (1) When they are placed in a drop of fresh water their pro- 

 toplasmic contents break up into the constituent zoospores, which 

 after escaping from the sporangia germinate readily within half an 

 hour. (2) They may give rise to one or more short germ-tubes form- 

 ing secondary sporangia, which may either form zoospores or tertiary 

 sporangia at the end of short germ-tubes. It is not unusual to find 

 three or four generations of sporangia linked together by short germ- 

 tubes (Plate V, Fig 1). This mode of germination is generally 

 found in old cultures and in those not kept in pure water. (3) They 

 germinate conidially giving rise to a mycelium. 



In cultures and on inoculated castor fruits a second spore form 

 has been found, the " resting " conidium or so-called " chlamydos- 

 pore. This " resting " form of conidium has been observed in the 

 Cacao Phytophtkora by Eorer 1 and apparently also by Petclr, and in 

 Pythium palmivorum* by Dr. Butler. The "resting" conidia are 

 usually spherical, thick and smooth walled, yellow in colour, terminal, 

 lateral or intercalar, 20-60^ in diameter and contain a lot of oil 

 globules (Plate V, Figs la and 7 to 13). Intercalar " resting " conidia 

 are formed in two ways. (1) In the course of a hypha, swelling takes 



1 Rorer, J. B. loc. cit., p. 13. 



2 Petch, T. Cacao and Hevea Canker, Cir. and Ayric. Journ. Royal Bot. Card., 

 Ceylon, V, No. 13. 1910, p. 15.'}. 



3 Butler, E. J. loc. cit., p. 255. 



