sided^ (Fig. 336, A,B). The two rows of segments here form an elevated vegetative 
cone, at the base of which the rudiments of the leaves first appear at the height of the 
fourth or fifth segment. The two edges of the apical cell are directed upwards and 
downwards (on the obliquely ascending shoot). The relationship of the leaves to 
the segments has not yet been entirely made out. The two leaves of each pair arise 
obliquely, one above, the other below, and alternately right and left where the pairs 
cross obliquely, by the outgrowth of zones of cells, each of which embraces about a 
fourth of the circumference of the stem. Divisions then take place in these cells 
which are directed obliquely upwards and downwards, and a row of apical cells is 
thus formed, by means of which the growth of the leaf is continued (Fig. 336, A). 
The branching of the shoot is effected by a second two-edged apical cell being 
formed from the youngest segment (Fig. 335, C, D), a wall being developed in it 
which is convex to the existing apical cell and which intersects the primary wall 
below. The two shoots which are thus formed grow right and left of the previous 
Fig. 336>— Apex of the stem oi Selagiiiella Marte7is2i (after Pfefier) ; A longitudinal section of the end of the stem with 
the first rudmient of the leaves ; B apex of the stem seen from above ; C formation of an apical cell seen from the side ; 
D the same seen from below. The primary walls of the segments are denoted by darker lines ; the segments themselves 
are numbered with Roman figures. 
direction of growth, and all the successive branchings take place in one and the 
same plane. 
The Roois. All the species of Selagtnella possess true roots ; but in some, 
as 6". Martensii and Kraussiana, they arise on a structure which Nageli calls the 
Rhizophore, and which has no root-cap. In S. Kraussiana the rhizophores spring 
from the dorsal side of the stem, nearly at the base of the weaker of each pair of 
branches, curl themselves round it, and then grow downwards; it is only rarely 
in this species that two of these organs arise near one another. S. Martensii^ on the 
other hand, forms at each branching two rhizophores, one on the dorsal and one on 
the ventral side (the plane which passes through them is perpendicular to the plane 
of branching), but usually only the ventral one undergoes further development, while 
the dorsal generally remains in the form of a small protuberance.^ The rhizophores 
' [Treub has shown (Recherches etc. sur le Selaginella Martensii) that the form of the apical cell 
is very variable ; it is sometimes two-sided and sometimes three-sided in branches of the same plant.] 
