THE HIGHER CRYPTOGAMIA. 333 



figs. 21 — 23,) and which becomes rapidly wider by longitu- 

 dinal divisions,* first of the apical cell, and then of the 

 other cells of the fore-edge (PL XLV, figs. 20, 24,) of the 

 flat and leaf-like structure. This excrescence is the first 

 leaf. 



Soon after its appearance, a shoot of the fore-end of the 

 embryo is observable underneath its place of attachment 

 and before its median line. This shoot appears at first as 

 a hemispherical, slighty protuberant, cellular excrescence. 

 The arrangement of the cells of the embryo, especially if 

 observed in a longitudinal section through the median line 

 of the first leaf (PI. XLV, fig. 21), leads to the conclusion 

 that the excrescence was formed by the division of the 

 apical cell of the fore-end, first by a septum inclined towards 

 the first leaf, and then by a septum inclined in the opposite 

 direction. f These divisions are repeated in regular suc- 

 cession in the terminal cell for the time being, which cell 

 has the form of a segment of a sphere. This excrescence 

 is the principal axis of the germ plant. On the right and 

 left of it the margin of the lamina of the first leaf is deve- 

 loped into ear shaped appendages (PI. XLV, figs. 24, 25 a ~ c ). 

 Whilst these — extending beyond the end of the principal 

 mass — approximate more and more nearly to one another, 

 the still leafless apex of the leafy shoot ramifies twice, 

 sending out the more slender ramification (normally) first 

 to the right and then to the left J (PI. XLV, fig. 25 f£ " c ). 

 In the mean time the cells of the hinder end of the embryo 

 only multiply to a small extent. That end is now attached 

 at right angles in the form of a stalk-like prolonga- 

 tion, to the flat, proportionably thick, first leaf, which forms 

 the principal mass of the embryo (PL XLV, figs. 22, 26, 

 2o a ' b ' c ). Its cells are now throughout almost cubical. 



This growth of the first leaf ruptures the prothallium 

 (PL XLV, fig. 26). By the expansion of the cells of the 

 hinder end of the pro-embryo, — which expansion takes 



* These divisions are interpolated between the divisions produced by septa 

 inclined to the outer surfaces. 



f The succession of the division may be inverted (PI. XLV, fig. 19). 



% The observer is supposed to look from above upon the fore-surface of the 

 first leaf. 



