Laffkkty — Disease of Cultivated Flax. 273 



EXPLANATION OF PLATES. 

 Plate VIII. 



FIG. 



1. Naturally affected flax seedlings, seen from above, showing dark diseased 



areas on the cotyledons, attacked by Polyspora lini, which represent 

 the earliest stage of " browning." (Slightly enlarged.) 



2. Portions of stems of mature flax plants, showing various stages of the 



"browning" disease. That on the extreme left shows spotting of the 

 leaves only. Death of the leaves and infection of the stems is evident 

 on the remaining four, (x J.) 



3. Bottom row : healthy flax fruits. The upper two rows show affected 



fruits in various stages of attack. (Natural size.) 



4. Transverse section through a mature flax stem aflected with " browning." 



The dark diseased cortical and epidermal tissues extend nearly, but not 

 quite, around the stem, (x 30.) 



5. Five naturally affected young flax plants, showing stages in the develop- 



ment of " stem-break." The two on the extreme left show cotyledonary 

 infection only ; the two on the extreme right have their cotyledons 

 destroyed, and infection of the stems at the node has occurred, with 

 incipient break. The central one shows an intermediate stage. 

 (Slightly reduced.) 



Plate IX. 



1. " Stem-break " produced by placing conidia of P. lini from a pure culture 



on the cotyledons of seedlings. In all cases the stems became 

 attacked, and fracture of the stem, with subsequent upward bending, 

 is well marked in four cases. (Slightly reduced.) 



2. Stellate form of growth of P. lini on wort gelatine from a single coni- 



dium ; culture five days old. The masses of conidia are seen along 

 the radiating hyphae, which are, however, invisible in the photograph, 

 (x 30.) 



3. Conidia formation in P. lini, from a five-day old pure culture on a wort 



gelatine film, (x 270.) 



