500 Shove.—On the Structure of the 
it is stated that the roots of the Marattiaceae have one large 
apical cell, which is surrounded by numerous segments ; these 
are similar in form and function to the apical cell, but show 
no transverse divisions. 
This view of the apical cells is different from that of 
Russow, and is elaborated by Holle 1 in a paper published 
in 1875. Holle recognizes three forms of apical growth: 
firstly, the subterranean roots have a four-sided apical cell, 
from which the neighbouring cells can be clearly seen to 
arise; secondly, somewhat thicker roots have an irregular 
apical cell, between which and the neighbouring cells no 
hard distinction can be drawn ; and, thirdly, the large aerial 
roots have no apical cell, but growth occurs by numerous 
initial cells in the manner described by Russow. 
In a paper by Schwendener 2 in 1880 we find the view that 
a median section of the root-tip shows only two apical cells, 
and hence that apical growth is carried on by only four 
initial cells. 
Bower 3 confirms this statement, and further says he has 
traced in a branch-root the development of four initial cells 
from a single cell of the endodermis. 
The most important paper on the root-apex is that by 
Koch,‘ Ueber Bau und Wachstum der Wurzelspitze von Angio- 
pteris evecta, Hoffm. 4 ’ 
The view here expressed is that no persistent apical cell is 
present at all, but that one of four particularly large cells 
assumes the function for a time. It becomes pressed into the 
organic centre of the root, and divides into four; three of 
these go on dividing and form meristematic tissue, but the 
fourth increases in size without division, and, being by pressure 
made to occupy a central position, repeats the process just 
described. 
This method of growth occurs in small earth-roots; in the 
thicker earth-roots and in the large air-roots the above- 
mentioned four-celled complex indeed exists in the extreme 
1 Holle (’75). 2 Schwendener (’80). 3 Bower (’85). 
4 Koch (’95). 
