440 



was planted on the opposite side of the greenhouse. The foliage of these 

 two plants became intertwined as they grew into the upper part of the house. 

 The Royal Muscardine plant had no trace of disease. 



These instances show how differently varieties behave in the same 

 environment, and how individual diseases in the same variety may be 

 explained. 



In regard to the different behavior of different vines, reference should 

 be made to a study by Fr. Muth\ who observed the production of intu- 

 mescences after spraying the leaves with copper compounds, while, for ex- 

 ample, the early red Veltliner and Muscat St. Laurct show^ no swelling. 

 Morillon panache, Madeleine Angevine and the Blue Ox-eye were very 

 greatly affected. 



In another similar case, Noack- found that the disease decreased when 

 water was withheld. 



The occurrence above described does not correspond with the phe- 

 nomena found on Ampelopsis hederocca''. In this plant Tomaschek found 

 bead-like structures on young branches, petioles and leaf veins, and espe- 

 cially on the outer side of the side leaves. The beads were very small when the 

 illumination was insufficient and dried up in the autumn. They were formed 

 below the stomata even in the very young parts, since the cells surrounding 

 one cavity grew down into it and forced up the epidermis by an increase 

 in size. In the autumn and winter true lenticels with a cork formation were 

 found, instead of these outgrowths. 



In addition to the instances already described and those to be men- 

 tioned further on of disease manifesting itself on greenhouse plants, I will 

 now report on the behavior of one of the Gramineae. 



On the island Riigen, among vigorously growing oats, plants were found 

 showing abnormal growth. A cross-section of the lowest node, covered 

 with dirt, is illustrated in Fig. 78. The centre of the node exhibits the well 

 known irregular course of the vascular bundles (g) and the primordia of 

 a root (w) ready to break through the distended bark of the node. In this 

 bark covering r indicates the normally formed part, while at r' the subepi- 

 dermal parenchyma cells are already beginning to elongate radially. The 

 excessive elongation increases at j to a decidedly tube-like character and 

 afifects all layers of the bark near the root just coming through. This dis- 

 tends the epidermis very greatly, and, as its cells do not take part in the 

 process of elongation, it finally begins to separate in different places (c). 

 The leaf blade at rr shows an external injury from grazing cattle which 

 extends deep into the node. The tissue is considerably browned, the 

 vessels, as far as the middle of the node, are partially filled with gum. The 



1 Muth, Fr. tJber die Beschadigung der RebenbUitter durch Kupferspritzmittel. 

 Mittel. d. Deutsch. Weinbau-Vereins 1906. 



- Noack, P^r., Eine Treibhauskrankheit der Weinrebe. Gartenflora 1901, p. 619. 



3 Tomaschek, Dber pathogene Emergenzen auf Ampelopsis hederacea. 6sterr. 

 Bot. Zeit. 1879, p. 87. 



