452 



scales in its yellow , uncommonl}- brittle walls, breaking into sharply pointed 

 pieces and in the wide lumina of the cells, while that of the healthy ones, 

 with their somewhat swollen, thick, colorless walls, ha\e sunk together until 

 the lumen disappears. All traces of starch have disappeared from the 

 yellow-walled tissue, which sometimes traverses the scale, is suberized, and 

 pushed up by the subsequently i)roduced cork cells and from the colorless 

 surrounding tissue. 



After the diseased, dry bulb scales have been removed, one notices that 

 the still perfectly white, succulent scales, normally extending to the neck of 

 the bulb, have begun to dr}% beginning at the top. Here the tissue loses its 

 natural smoothness and turgor, so that gradually the scale has a folded 

 appearance, due to the collapse of the cells which lie between the more 

 prominent vascular bundles. Besides this, the edge usually becomes yel- 

 lowish. At the same time, on the deeper parts of the fleshy, white places in 

 the scales, glistening from turgidity, appear small, longish, glassy, trans- 

 parent, yellowish spots, protruding shghtly above the upper surface. These 



Fig. 89. Cross-section tlirougli a scale of a hyacinth infected witli skin disease. 



(Oriff.) 



increase in a few days and almost at once become more noticeable because 

 of the yellowish juicy edge. Then, however, the change advances more 

 slowly, since the outpushing occurs only gradually more distinctly and its 

 centre becomes whitish with a dry membrane and longitudinal folds ; with 

 increasing age, the centre becomes depressed and finally the scale seems 

 perforated. When treated with sulfuric acid the upper lamellae, lying 

 directly beneath the cuticle (Fig. 89 /) of the somewhat thickened epidermal 

 cells, swell up markedly and at limes mycelium may be found in them. 



A cross-section through the diseased scale (Fig. 89) shows at b an older 

 pustule and on the left of this a younger one. In the discolored epidermis, 

 the walls are swollen and this process of swelling and suberization (vk) m 

 the older leaves has already advanced through the whole thickness of the 

 scale. Here the fleshy, starchless parenchyma, which at the beginning (p) 

 was found to be still colorless and with a normal arrangement, has col- 

 lapsed like cords and formed hardened places with irregular openings (s). 



In the cells directly beneath the outpushed epidermis, there are no nuclei, 

 while they are present in the next inner cells, but brown in color. In the 

 epidermis, cork cells are produced, while the parenchyma lying beneath gives 



