191 



tube which pierces the cell wall and penetrates to the oosphere. 

 the protoplasm of the hypha then passing into and mixing 

 with that of the oosphere, through the short connecting tube. 

 The oosphere is then said to be fertilized and is called the 

 oospore. These spherical oospores soon develop a hard pro- 

 tective cell-wall and are capable of retaining thejr vitality 

 and power of germinating for a considerable period. These 

 spores find their way from the decaying tissues of the seedlings 

 into the soil and, if seed is sown in the same soil, the new 

 crop of seedlings is almost invariably severely attacked by 

 the disease, the oospores in the soil germinating and producing 

 hyphse which then proceed to branch and form conidia as 

 before. This fungus is as a rule only destructive to seedlings, 

 young plants one year old and upwards being rarely injured. 

 It is also capable of living in the soil for a long time as a 

 saprophyte and thus can exist independently of seedlings, 

 although it is always ready to resume its parasitic mode of life 

 on any suitable seedlings it may meet with. 



As in P. infestans moisture favours the spread and deve- 

 lopment of the pest; consequently shading the seed beds is 

 inadvisable as this would prevent the rapid evaporation of 

 moisture. Spraying with Bordeaux mixture will aid in pre- 

 venting the spread of the disease. Isolated specimens of 

 diseased seedlings should be carefully removed and burnt, 

 care being taken not to infect fresh seedlings by shaking of? 

 the conidia. If a considerable number are affected the best 

 way of preventing the dispersal of the conidia is to cover 

 the patch carefully with soil. People passing through the 

 seed-beds may convey the conidia on their clothes, or boots, 

 to healthy individuals which should be avoided as far as pos- 

 sible. Seed-beds must be frequently inspected so that timely 

 measures may be taken to check the disease. A seed-bed 

 which has been attacked should not be used again for seed- 

 lings of the same species. In some cases good may be done 

 by burning rubbish on the infected seed-bed, sufficient heat 

 being produced to kill the spores in the soil. 



168. This fungus is also known (2) Fames 



by Hartig' s name of Tmmetes radiciperda. In Europe it has f ** 

 been found to attack Pinus, Picea, Abies, Juniperus, Thuja, the species 

 Beech, and other dicotyledonous trees. It is most destructive to attacked, 

 conifers, and in India it is at present best known on account 

 of the damage done by it to the Deodar, Cedrus Libani var. 

 Deodara, which it attacks and kills. The fungus is frequently 

 seen in the forests of Jaunsar. 



