33 



case it was only necessary to allow the section, just as it came from 

 the dissecting stage, to lie sealed in water for twenty-four hours or 

 thereabouts to obtain spores in a state of germination. The spores, 

 under such conditions, were either produced anew by the mycelium or 

 were loosened so as to float out into view. (Fig. 52.) 



The mycelium of the fungus, when freshly torn away and floated out 

 where it could be seen, was often very fine, not much exceeding 

 n micromillimetre in diameter. 



If pustules are sectioned and placed in a sealed water-culture, the 

 neighbourhood of the cut perithecium, after about forty-eight hours, 

 is sometimes the scene of an active production 

 of sporules. These originate at first from Oft t) 



that portion of the fungus inside the pustule; 0Q 



and then, getting free, increase outside by x4oo 



division. In one instance I observed that pig. 53. secondary growth of 

 this growth took place in a slightly gelatinous *Xu! e fr found "$?*$ 

 substance which was clearly concentric with f c * b > water-culture after 



mi -i-ii forty-eight hours. These 



the CUt perithecium. The Spores produced by spores were enveloped ia 



this process are illustrated in Fig. 53. After 



forty-eight hours, this growth of sporules begins to show signs of 

 failure ; the later spores produced by division are much smaller, and 

 are more attenuated. Adjoining are some measurements of spores 

 arising in the manner just described. 



Before being ruptured, the cavity of 

 ii-Ox3-OH Average, 9- x 2*8^ the perithecium is capped by tissue 



3. 8-0x3% I (disregarding Nos. that in cross-section appears nearly 



4. 7-Ox2-5 A if 5 and 6, which black : so also the bottom of the cavity 

 6 x o'^ \ W6re kte gr WthS) " when viewed in cross-section is dark 



D. oOXU^M^ Till mi ii 



red or nearly black. I he whole is 



underlaid by a stratum of somewhat columnar cells which have ap- 

 parently originated through an attempt on the part of the plant to 

 counteract the parasite. Such columnar tissue is not to be seen else- 

 where in the section that is to say, in the more or less normal 

 tissue beyond the borders of the pustule. (See Fig. 32.) 



When material is scraped from the cracks present in well-developed 

 scab, and the pulverulent matter thus obtained is placed in water 

 under the microscope, it is easy to find in it X(VOO 



the same spores that are characteristic of the 

 pustules. They are usually found in such 

 considerable numbers that the conclusion sug- 

 gested is that the reproduction of the fungUS Fig. 54. Spores obtained under 



takes place quite as vigorously in the fully- ^ b d*!SHW^ 

 formed scab as in the pustules which precede Sbelfc'the text** de " 

 it. (Fig 54.) 



At the same time one finds among the material derived from scab 

 in this manner large numbers of yeast cells, and these show up with 

 such regularity as to constitute a marked microscopic feature of this 

 phase of the disease. Especially abundant are these yeast cells in 

 cultures inoculated from loose scabby material. 



36567 c 



