127 



small normal one. Homooplasio is opposed to the phenomena of 

 the g:^.ant gr owth here descritied in so far that its products ac- 

 cordingr to the" definition always bear the character of abn ormal 

 tissue-formations. The latter will he the case, if the""9ver-- 

 production of the normal elements occurs only in narrowly limi- 

 ted places, or if only one of the tissue forms, or scattered 

 forms, oomposing,a leaf, a stalk, etc., are developed in ab- 

 normal abundance . 



Prom the ifeutset it. must be noted that here. Just as in the 

 other groups which we have set up, no absolutely sharp demarca- 

 tion can be drawn and that abnormal formations are not lacking, 

 which furnish at the same time a transition from the phenomena 

 tf giant growth, the study of which is the task of morpholo- 

 gists, to homooplasias, which will be reported more closely 

 in the following, 



1, Localized tissue excrescences of an homooplasticchar - 

 acter . composed of the same histological elements as the orig- 

 inai, are rare. A cross-section through a sugar beet ( Beta 

 yulgaris) is reproduced here, which continued its growth in 

 thickness ebnormally even in the second year, thereby develop- 

 , ing several ridge-like tissue excrescences extending longitud- 

 inally. These extensive ridges are composed of normal layers 

 of tissue. In figure 57, the concentric normal cambial rings 

 are indicated in the center as well as those newly produced in 

 (140) the ridges. In a case closely investigated by de Vries2 the 

 formation of new cambial rings outside the latest ones of the 

 first year, coincided with an arrestment of activity. The 

 rings of the first year as well as the accessory ones of the 

 second year were also only slightly lignified. The causes of 

 the excrescences lie supposedly in an abnormally increased sup- 

 plying of material. 



Similarly the tissue excrescences, occurring on the leaves 

 of Aristolochia Siphp and others, have been known for a lottg 

 time^ On the under side of the leaf blade, along the ribs, 

 wing-like ridges, no thicker than the leaf, are. produced, which 

 like the normal leaf-blades are composed of epidermis and meso- 

 phyll and aye traversed by vascular bundles. The question as 



^ Virchow, (Celltilarpathologie) uses the word hjrpermetry 

 in a similar sense. 



^ Ueber abnormale Entstehungsekundare* Gewebe. Prings- 

 heito's Jahrb. f. wiss. Bot., 1891, Bd. XXII, p. 45. There also 

 statements on some of the tissue fcrms subsequently discussed 

 by us and on the results of the "lengthened life-period". 

 Further Rimpau, DasAufsohiessen der Runkelrtiben. Landwirtsch. 

 Jahrb., 1876, Bd, V, p. 43.,, Briem, Strohmer and Stift, Wurzel- 

 kropfbildung bei d. Zuckerrube. Oest.-Ung. Ztschr. f. Zuckerm- 

 distric etc., compare also Ztschr. f. Pfl.-Kr&nkh. , 1892, Bd., 

 II, p. 239. Caspary observed on Bra ssJoa Hapus (Sine Wruck© 

 mit laubsprossen aus knolligem Wurzelausschlag . Schrxften Phys.- 

 Oeken. Ges. Konigsberg, 1873, p. 109), tuber-like swellings upon 

 which were buds and which could develop bunched shoots with 

 malformed leaves. The disease is hereditary as Casparj?- has 

 shown. (Hvpels described swellings on Beta of apparently vary- 

 iiig structure. Notes ^athologiques, C. R, Soc. Bot. Belgiqu», 

 1837,' T. :xrVI, p. 183. Therein citations of literature regard- 

 ing parasitic SKellings of a similar kind. 



