376 GENERAL PLANT PATHOLOGY 



vision of the cells there are produced tissues, the single elements of which 

 have no resemblance to normal ones. Size of cells is of relatively little 

 interest in the study of these abnormalities. More important are cata- 

 plasmic and prosoplasmic tissues, which are formed in heteroplasia. 

 Cataplasmic tissues are those which are more simply constructed than 

 the corresponding normal tissues, while prosoplasmic tissues are those in 

 which we can see processes of differentiation in the formation of their 

 single cells and in the distribution of their different elements, which are 

 not manifest in the formation of the corresponding normal tissue. 



The material illustrating the various kinds of heteroplasia may be 

 treated of under the following heads: 



1. Correlation-heteroplasms 1 



2. Calluses \ Cataplasms 

 Heteroplasias 3. Wound- wood J 



4. Wound-cork 



Galls 



I . Correlation-heteroplasms 



(a) Cataplasms 



(b) Prosoplasms 



This term is applied to cases where the normal growth of any plant 

 is arrested at its vegetative points by any causative factors whatsoever, 

 and where under the stimulus of the unused nutritive materials some part 

 of the plant develops abnormal growth and tissues. Vochting has 

 studied this subject in all of its details. He found that decapitation 

 of sunflower plants resulted in the production of tuber-like swellings 

 on the roots and that in the aerial runners of Oxalis crassicaulis filled 

 with reserve materials that removal of the apical cells and all axillary 

 bud cells resulted in the formation of swellings on the leaves and 

 internodes. According to Vochting, the parenchyma participates, also 

 the vascular bundles, which have fewer ducts than the normal ones. 

 The sieve tubes, however, are richly developed and extensive funda- 

 mental tissue outgrowths are found between bast and wood. The first 

 experimentally produced correlation-heteroplasms were made by Sachs. 

 He cut off all the vegetative points of pumpkin plants. He found, as a 

 result, that the embryonic root cells present in the stem at the right 

 and left of each petiole grow out into short-stalked tubers, as large 

 as marbles, in which the root cap and vegetative point are absent and 



