6 INDUCTION, DEVELOPMENT, AND HERIT ABILITY OP PASCIATIONS. 



or maroon color in the secretory cells of the parts exposed to injury. 

 Simple fasciations when sectioned show the traditional structure of Hat 

 stems and do not vary from the normal except in outline. 



Sections of ringf-f asciations , as diagrammed in plate iv, series 3, follow 

 closely the description of Nestler (8) for I'cronica longifolia in having, 

 besides the primary bundle-ring", a second bundle-ring bordering the 

 cavity of the funnel. This ring originates as a group of meristematic cells 

 in the center of the medullary parenchyma. Gradually successive groups 

 of meristem appear, arranged in a circle, and these differentiate into typical 

 bicollateral bundle -groups. The earliest group consists of several undif- 

 ferentiated cells, which show their first trache;c some sections above their 

 initial appearance. The latter .croups in their earliest stagv consist of 2 

 cells side by side, a trachea and a nucleated proscnchymatie cell. The 

 parenchyma cells in the center of the pith below the first signs of the ring 

 are smaller than the peripheral cells and more crowded together. The 

 phyllotaxy of the stem is already changed from the normal below this point, 

 so that the loss of definite arrangement is seen to precede the formation 

 of the meristems. The secondary bundle-groups gradually increase in si/.e 

 and merge together into the ring; there appears in the center of the pith a 

 lysigenous cavity, which is the beginning of the hollow of the funnel, and 

 further differentiation produces an internal epidermis, cortex, and stereome 

 ring, in sequence the exact reverse of the primary arrangement in the 

 periphery. At the apex the two bundle-rings merge into one. When the 

 side of the funnel breaks, the two rings unite at the break and surround 

 the elliptical pith of a simple flat fasciation. As there are leaves and flowers 

 within as well as without the funnel, there are leaves and flowers on both 

 sides of the banded stem. 



The structure of the groove fasciation of the wild O. bicmiis, shown in 

 plate iv, series 1, presents a case analogous to this. At an early stage of 

 development a portion of the cambium is destroyed, the bundle-ring broken 

 through, and the space is filled with parenchyma. The expansion and 

 increase of the undisturbed cells results in the constriction g-, which is 

 the external sign of the groove. In the interstice in the ring a meristem 

 develops in the parenchyma, succeeded by other meristems lateral to it. 

 These differentiate into a line of bundle -groups which merge with each 

 other and with the primary ring. During this process the stem flattens, 

 although it is circular when the meristem appears. The flattening is a 

 slow and at first imperceptible process, and the beginning of the alteration 

 must be sought far below the point where it is visible to the naked eye. 

 The distance of the open groove from the tip is 17 to 26 cm.; the stems arc 

 flat and broad 12 to 19 cm. from the tip; the meristem begins from 2 to 

 4cm. below the opening of the groove. The early stages of the process may be 

 followed by a reference to plate v, figs. 1 too. The origin of the meristem 



