683 



fields of a leaf often appear distended, the green ones wrinkled, or blistered. 

 The stems also at times, in the non-pigmented part, show some shortening, 

 as is proved by the variegated Kerria japonica, of which green shoots on 

 the same stem and of the same age are at times half a meter taller than 

 those bearing white leaves. Sambucus, Weigelia and others, behave in 

 this way. 



in my opinion, albinism is a form of arrested development which occurs 

 more rarely in wild plants but to an increasing degree in cultivated ones 

 and manifests itself in the poorer nourishment of the different tissue ele- 

 ments. The result of this is that, either the chlorophyll apparatus does not 

 mature at all, or soon falls victim to destructive enzymes. The lack of any 

 accumulation of resen^e materials, or, at most, a scanty one, is connected 

 with this and explains the increased collapsibility of the tissues. 



Of the causes producing albinism, the pressure conditions in the bud 

 should come first under consideration which arrest the development of the 

 conducting system and thereby hinder the sufficient filling of the cells with 

 plastic material even in the embryonic condition. This would explain the 

 phenomenon of the sudden development of a non-pigmented shoot from the 

 bud of a plant which had been green up to that time. In regard to cultural 

 influences, experience shows that a relative excess of light acts favorably, 

 for we see that often a condition of pure white leaves occurs very inten- 

 sively with direct, strong insolation and is retained longest, but decreases, 

 when shade and a sufficient supply of water and nitrogen give the leaf time 

 to develop more slowly and let its vegetative functions act longer, i. e., 

 preventing a premature end of life. 



Timpe^ cites in his latest work a phenomenon which has been repeat- 

 edly tested experimentlly. He repeated the experiments first described by 

 Molisch- with the white and green variegated species of Brassica oleracea 

 acephala and obtained the same result, viz., that the brilliant white color of 

 the leaf surfaces, which reaches its greatest development in winter in a 

 cold frame (up to February), decreases almost at once and finally disappears 

 if the plants are brought into a warm place. Molisch transferred white 

 variegated plants from the cold frame at 4 degrees to 7 degrees C. into a 

 hot bed at 12 to 15 degrees C. All the leaves already formed turned green 

 in from 8 to 14 days ; those newly formed appeared green at once. Returfied 

 to the cold frame, the specimens again formed leaves variegated with white. 

 Here belongs also Weidlich's statement^ that Selaginella Watsoniana must 

 be cultivated in a temperature of 10 degrees C. if it is to form white tips. 

 In these cases, therefore, the increase in the vegetative functions, producing 

 the loss of albinism, is conditioned by the increase of heat; while in other 

 cases, according to the nature of the plant and other local nutritive condi- 

 tions, the variegated leaves can be brought back to the optimum of their 



1 Tempe, Heinrich, Panachierung und Transplantation. Jahrbuch d. Hamburg:. 

 wis.s. Anstalten XXIV, 1906, Beiheft'^3. 



2 Ber. d. Deutsch. Hot. Ges. XIX, 1, p. 32. 



3 Gartenflora 1904, p. 585. 



