422 On the Fecundation and Development o/Marsilea. 



increases between the first leaves. The increasing covering of 

 the bud with hairs, and the liability to injury of the young 

 vegetative point, render the observation of the further develop- 

 ment difficult. But all the facts hitherto observed go to prove 

 that the apical cell continues its further evolution in the same 

 fashion, even in the growing stem-bud of the old plant. The 

 leaves always appear exactly bipartite, somewhat approximated 

 on the upper side of the horizontal axis. It is consequently to 

 be supposed that all of them, like the first, originate only from 

 the cells of the two upper series which proceed from the apical 

 cell, whilst the third series only furnishes the commencement of 

 roots and internodial cells. 



This whole process of cell-division therefore shows that the 

 first perpendicular wall divides the germ into the primitive cells 

 of the stem and root, and that the ideal primary axis of the free 

 germ is consequently to be regarded as horizontal. From the 

 stem-cell the first septum separates the first leaf, which has the 

 import of a cotyledon. The second furnishes a piece which, as 

 it only forms, in common with a divisional cell of the root of 

 the same order, a parenchymatous body situated laterally to the 

 axis, must be regarded, not as a metamorphosed leaf, but as an 

 internodial part, like many which subsequently issue from the 

 apical cell of the stem alternately with the foundation-cells of 

 the leaves. Consequently the first root also, which lies exactly 

 in the line of the posterior extension of the main axis of the 

 stem, acquires the position and direction of a main root. On 

 the contrary, the view that the foot is essentially the aborted 

 primary axis, and that the first root and first bud are only ad- 

 ventitious organs, is supported neither by the position nor by 

 the sequence of the septa in and between the constituent founda- 

 tion-cells of the germ. 



The first germ-leaf is situated in the median line of the germ, 

 the subsequent ones to each side. Between the first and second 

 leaves the divergence is about = \ ; the rest follow under a 

 divergence of ^, whilst the spiral continually becomes closer. 

 On the other hand, the division of the apical cell itself passes 

 reipidly into an homodromous spiral with a divergence of ^. 

 After the second leaf the cell-multiplication no longer com- 

 mences with a perpendicular septum, but rather with walls 

 .directed towards each other laterally. Their development is 

 similar to that known to occur in other Fern-leaves. They 

 gradually attain to a greater extension, which only reaches its 

 term about the tenth or twelfth leaf. 



The prothallium follows the development of the germ itself 

 by an independent growth, moulding itself upon the form of the 

 germ. At last the rapidly growing leaf bursts it above, and the 



