457 



Fig. 90. At the right side of the figure, indicating the manner of growth, is a 

 reduced piece of the stem of Cereus nycticalus, which, blackened and softened at 

 the tip, shows a piece of tlie baric loosened by pressure of the fingers. On its lower 

 part are found deep bowl-like wounds which have been, healed- The upper drawing 

 of the structure shows a cross-section of a bowl-like wound which is being healed. 

 The lower drawing gives the new structures and tissue differentiations, which take 

 place during the process of healing the wounds. (Orig.) 



M pith. H wood. R bark, s normally placed ducts, .g-' di.splaced duct.s, b groups of dead, hard ba.st of 

 the outer bark, enclo.sed by bark, b^ groups of young hard bast of the outer bark, wr dead edge of the 

 wound of the older bark (R). The old tissue is separated from the healthy tissue by a layer of plate- 

 like cork cells (/). w and « new bark differentiated from the wound callus. 



disease, while in the following year, \\'\\\\ the new planting of foliage plants 

 and with accordingly increased humidity in the air, it reappeared to a great 

 degree. For this reason, I would like to consider the phenomenon as a 

 direct result of excessive humidity. 



Methods for checking this are self evident. In one case, besides the 

 increased supply of light and air, the addition of plaster to the soil has 

 proved advantageous. 



We have devoted considerable space to intumescences and related 

 phenomena in order to point to their importance. Greenhouse plants are 

 chiefly considered and repeated observations have shown that most numer- 

 ous diseases may be traced to the act that the natural dormant period of the 

 plant was not considered and the plants were stimulated to untimely and 

 therefore abnormal growth, by a high degree of heat and moisture. 



