350 HOFMEISTER, ON 



to explain them I must speak, in anticipation, of the process 

 of development of vigorous roots of plants some years old 

 (PI. LII, figs. 25). 



The one cell which is situated underneath the place of 

 insertion of the scale of the first frond, and is surrounded 

 by its sheath- like base, is the punctum vegetationis of the 

 (secondary) principal axis of the plant ; the terminal bud 

 of the embryo is at this time limited to this one cell. As 

 the bud is developed the cell divides by septa inclined 

 alternately in opposite directions. The lines in which these 

 septa cut one another are at right angles to the front surface 

 of the first leaf. 



Until the plant is fully formed the growth of the stem is 

 caused by the constantly repeated uniform division of the 

 apical cell. The direction of the septa produced in it re- 

 mains always the same, viz., at right angles to the major 

 axis of the ellipsoidal transverse section of the stem, and 

 parallel to the furrows of its under side. 



The mode of multiplication of the cells of the second de- 

 gree which are thus produced, resembles in general that of 

 the same cells of the first leaf above described. After the for- 

 mation of the second secondary cell, the second leaf is pro- 

 duced on that side of the end of the principal axis which is 

 turned away from the first leaf, by the multiplication of the 

 youngest cell of the second degree of the stem-bud. The 

 mode of its development corresponds entirely with that of 

 the first (PI. XLVII, figs. 2, 3). Its formation commences 

 immediately after the first root becomes visible ; during its 

 development the upward growth of the surrounding sheath 

 of the first leaf ceases for some time. When the second 

 leaf has attained a height of from three to four cells, a re- 

 markable elongation of the cells of the first leaf which now 

 contain chlorophyll commences at the apex of the latter. 

 In consequence of the multiplication of its cells in a longi- 

 tudinal direction, the first leaf has by this time advanced 

 almost to the periphery of the prothallium. The leaf breaks 

 through the prothallium and appears in the form of a green 

 point outside the latter : it elongates itself very rapidly by 

 the longitudinal expansion of its cells, which proceeds from 

 the apex of the leaf towards its base, where cell-multiplica- 



