859 



trifugally, proves that they are, nevertheless, specifically heavier than the 

 cytoplasm. Therefore, the cytoplasm of the statocytes must have less specific 

 weight and must be very fluid, i. e. it must contain very few elements of 

 considerable consistency. Nemec also discovered peculiar cytoplasmic 

 accumulations in the statocytes of the root cap, which certainly represent 

 an especial reaction. 



If a young root is cut ofif above its zone of growth and not within it, no 

 regeneration but substitution takes place, for new lateral roots are produced, 

 of which those nearest the wound surface are caused by their geotropic 

 sensitiveness to grow down more perpendicularly than if they had developed 

 from an uninjured main root. This makes possible the utilization of the 

 soil layers for nutrition, which the perpetidicular, downward growing main 

 root would have traversed^ A fasciation of the lateral roots takes place at 

 times after injury, or removal of the main root. Lopriore- was able to 

 produce this fasciation artifically. 



Gnarly Overgrowth Edges. 



One universal characteristic in the overgrowth of wounds is that the 

 wood fibres do not always parallel throughout the new structure but are 

 often bent and twisted until at times they are looped. These variations in 

 the course of the fibres form what is termed "gnarly wood." The adjoining 

 figure of the overgrowth cap of an oak branch, from which the bark has been 

 removed, gives the best insight into this. The oak furnishes especially good 

 examples of a complete closing of large wound surfaces by overgrowth and 

 the luxuriance of the uniting wound edge not infrequently brings about the 

 condition where, for example, in sawed off, larger branches, the newly 

 formed tissue does not have a flat surface but one more or less strongly 

 convex, becoming hemispherical to spherical in form. In such overgrowth 

 caps small centres are often found, the so-called gnarl eyes (Fig. 203, a), 

 around which variously twisted wood fibres {p) are deposited. By the term 

 "gnarl eyes," however, actual buds are not understood but rather depressed 

 tissue centres, around which are deposited the wood fibres in the form of a 

 bowl and later serpentinely twisted ; in this way representing the "curly 

 grain" in wood. While a spear-like, woody excrescence appears where 

 actual eyes are produced, in gnarl eyes a deep depression is found formed of 

 parenchymatous tissue, often increased by the rounding up and separation 

 of the cells. Wood is deposited around this depression, normally composed 

 of wood cells, medullary ray cells and vessels. The abnormality lies only in 

 the bowl-like arrangement, recalling the gnarl tuber, and the frequent 

 occurrence of medullary ray structures greatly broadeited and« resembling 

 medullary spots, which at times can develop into secondary centres. 



1 Bruck, W. F., Untersuchung-en iiber den Einfluss von Aussenbedingnng-en auf 

 die Orientierung von Seitenwurzeln. Zeitsch. f. allgem. Physiolog-ie Vol., Ill, 1904, 

 Part 4. 



2 Lopriore, G., I caratteri anatomici delle radioi nastriformi. Roma 1902. Note 

 sulla biologia dei processi di rigenerazione delle cormofite, etc. Atti Acad. Gioenia. 

 Catania 1906, Vol. XXI. 



