210 PHYTOPHTHORA PARASITICA. 



higher plants. He considers this to be the only reagent for the 

 products of the transformation of compound pectic substances. 

 They are dissolved by the successive action of hydrochloric acid and 

 an alkali. As recommended by Mangin 1 the oospores were at 

 first boiled for half an hour with two per cent, hydrochloric acid 

 and then with two per cent, caustic potash for a long time ; after 

 each boiling they were thoroughly washed. The result was that 

 the outer thick coat of the oogonium was dissolved, exposing the thin 

 inner coat, which had swelled under the treatment. The oospore 

 was lying loosely in it. The sporangia and " resting " conidia had 

 considerably swelled. Iodine and phosphoric acid and the other 

 iodide reagents of cellulose stained blue or violet the swollen internal 

 wall of the oogonium. Eau de javelle completely dissolved the 

 outer thick wall in twenty-four hours. After treatment for an 

 hour or two, it became quite soft and allowed the cellulose stains to 

 reach the internal wall and the oospore. The outer thick coat 

 stained brown with acidified Bismark brown and the stain was not 

 washed away by acids and alcohol ; it also stained violet with alum 

 haematoxylin. The former reaction shows that it is neither lignified 

 nor suberised, for the stain given to lignin and suberin by Bismark 

 brown is washed out by acids and alcohol. When treated with 

 seven per cent, caustic potash for a week or so the outer coat is 

 completely dissolved and the inner coat is also completely dissolved 

 or almost so ; in the latter case merely a faint halo is visible round 

 the oospore. This halo becomes just visible by its taking a bluish 

 tinge with phosphoric iodide. This inner wall, therefore, is 

 probably composed of some soluble form of cellulose, similar to that 

 which has been found by M. Hofmeister 2 to stain with zinc- 

 ehloride-iodide and to be soluble in five or six per cent, of alkali. 



The composition of the outer coat, which is dissolved by seven 

 per cent, caustic potash after a long treatment, by eau de javelle 

 in twenty-four hours and by the successive treatment with hydro - 



1 Mangin, L. Nouvelles observations sur la membrane. Bull. Soc. Bot. Fr., XL, 1893, p. 273. 

 » Vide. Mangin, L. loc. cit., p. 278. 



