224 HOFMEIBTER, ON 



niary cell of the root agrees with that of the apical cell of 

 the stem, except that the side- walls of the former are more 

 strongly curved (PL XXXI, tig. 6 h ; PL XXXII, fig. 1 *). 

 The layers of the root-cap, which on account of the more 

 vigorous growth at their median point are convex outwards, 

 are developed from the cells of the second degree, which 

 latter are formed by the production of flat septa parallel to 

 the basal surface of the primary cell. The permanent main 

 portion of the root is produced by the continual division of 

 those cells which have the form of the third part of a 

 hollow cone. The latter cells are first arranged in parabo- 

 loidal layers, which in the one longitudinal moiety of the 

 root protrude for about half the length of a cell beyond the 

 layers of the other moiety of the root. In the cells derived 

 from the third oldest cell of the second degree, this symmetri- 

 cal arrangement is changed into a homogeneous one, whilst 

 transverse septa parallel to the primary septa appear in all the 

 cells of the layer (PI. XXXII, fig. 1 h ). The mode of dif- 

 ferentiation and formation of the axile vascular bundle, and 

 the delay which at first occurs in its longitudinal develop- 

 ment compared with that of the bark (a delay which is 

 afterwards compensated by expansion), are common to both 

 the root and the stem. 



Ramifications of the root spring from its vascular bundles 

 in the same manner as the roots spring from the cortical 

 vascular bundles of the stem. The roots of the second 

 degree, as well as their ramifications, which are not of 

 frequent occurrrence, are arranged in two lines. 



The greater the age attained by a shoot of the Eagle 

 Pern — whether such shoot proceed directly from a pro- 

 thallium, or from a bud, or whether it be the single branch 

 of a forked stem — the greater is the tendency to furcation 

 of its terminal bud. Ultimately, in really old individuals, 

 frond-formation ceases entirely on the furcate branch when 

 more strongly developed. Only the more delicate forked 

 shoots which are placed alternately to the right and to the 

 left bring forth fronds ; the first one being always in the 

 inner angle. The naked unbranched terminal shoots of 

 those plants whose sympodium (which has the appearance 

 of a principal axis) bears no fronds, is developed with ex- 



