QUAKTERLY CHllONICLE OF MICROSCOPICAL SCIENCE. 293 



tion of the old apical cell a second septum originates vertical 

 to the first and directed to the op})osite side ; this forms the 

 mother-cell of the second bifurcation. The lower portion 

 remains the basis of the bifurcation, and afterwards, by cel- 

 lular increase, gives rise to a special portion of the divided 

 stem — the '' ramification-node.'^ 



In Halopteris the apical cell produces, not branches exclu- 

 sively, but sometimes leaves, sometimes branches, according, 

 apparently, as tlie lateral septum cuts off a smaller or larger 

 portion of the apical cell. Here only a single new direc- 

 tion of growth takes place, only one septum is formed, the 

 old apical cell merely becomes deflected, but still remains as 

 apical cell. 



The adventitious buds originate from the joints; the 

 quadrant-cell ("innovation-cell" or '^ brood-cell'') which is 

 to give rise to one does not form any cortical cells. In some 

 of the lower genera these adventitious buds show a regular 

 arrangement, but in Cladostephus tliis is not the case. The 

 connection of the medullary tissue in the stem and adven- 

 titious bud is produced by the first medullary cells within 

 the rudimentary adventitious buds reaching to the centre of 

 the stem, and appearing as lateral branches of the medullary 

 region of the stem. Hence there does not exist, as in the case 

 of dichotomy, any " ramification- node" belonging in common 

 to both branches, but at the place of ramification a new first 

 joint belonging to the branch is laterally apposed to the stem- 

 joint. 



The leaves in Cladostephus originate exclusively from the 

 peripheral cells of the joints. The first peripheral cells which 

 are produced are the mother-cells of the leaves and of the 

 cortex. These cells behave as apical cells, and are divided by 

 transverse septa. The first of the cells so formed give rise to 

 the primary cortex of the stem, and may be designated "leaf- 

 bases;" their upper divisions appear to form a transition 

 between cortex and leaf, and may be described as the " basilar 

 node" of the leaf. Some cells of the basilar node may oc- 

 casionally grow out in a papilla-like manner, and form a 

 second leaf. These may give rise to whorls of " supple- 

 mentary leaves." By repeated radial subdivisions of the 

 cortical cells of the joints in Cladostephus the origin of the 

 leaves becomes deeply immersed in secondary cortex. The 

 further growth of the leaves takes place by subdivisions of 

 primary cells produced by division of the apical cell. In the 

 immersed basilar joints the division of tlie secondary cells 

 for the formatiijn of the cortical and medullary tissues are 

 analogous to those of the stems. In the free middle leaf- 



