288 Transactions British Mycological Society. 



generation but in each case the Swede rotted before any result 

 could be obtained. 



The internal tissue of an epicotyl, in this case the swollen 

 epicotyl of the Kohl-rabi, was used in the next series. 



Series 2 K. Started Feb. 12th. Conidia from sources shown. 

 One inoculation in each case. 



The last two series certainly indicate that, however far species 

 of Erysiphe may be specialised as to their hosts, the infection 

 powers are always constant within that host whatever part is 

 used for inoculation. This is specially noticeable if one traces 

 the genealogy of 2 K 5, which, starting as conidia from a " sub- 

 infection " on Marrow-stemmed Kale, passed two successive 

 generations on the internal tissues of Marrow-stemmed Kale 

 and finally produced conidia again on the internal tissue of the 

 epicotyl of Kohl-rabi; or the example of i S 2, which started as 

 conidia from a full infection on the uninjured epidermis of a 

 Swede leaf, spent one generation on the outermost cells of the 

 cortex of the Marrow-stemmed Kale stem, one generation on 

 the innermost layers of cortex and vascular tissues of the same, 

 and finally successfully produced a full infection on the internal 

 tissue of a Swede hypocotyl. In the latter case conidia from 

 I S 2 were, on Feb. 12th, inoculated on to "cut M.S.K. " again 

 and by Feb. 23rd gave a slight infection showing a few conidia 

 and distinct discolouration. 



The last series to be undertaken was to demonstrate the 

 infection powers of conidia from " subinfections " when in- 

 oculated on to the uninjured surface of various hosts usually 

 only bearing " subinfections," i.e. cultivated varieties of Brassica 

 oleracea. A few inoculations on to varieties of B. campesfris were 

 included as controls. 



In each case uninjured leaves in water under bell- jars were 

 used as hosts. 



The signs used have the following significance : — = Experi- 



