508 Uphof. — Contributions towards a Knowledge of 
is composed of three rows of cells, which are slightly thick-walled through 
secondary layers ; the thin -walled cortex is composed of three to four layers. 
Of the vascular bundle the phloem is in comparison stronger developed than 
the xylem ; the latter is composed of eight to ten tracheides, of which 
Fig. IX. S. rubella, i, cross-section of rhizophore ; 2, longitudinal section : some cells 
show mycorrhiza. 
about three to four belong to the protoxylem. Also in the root mycelia 
have been found. 
Selaginella haematodes. 
The rhizophores are fibre-like, 6 to 10 millimetres in length and J to 
millimetre in diameter. They only develop towards the base of the stem 
and never higher up. The epidermis, hypodermis, and cortex cells do not 
differ much from one another in size. The epidermis has a very thin 
cuticle, and with those of the hypodermis shows but slightly secondary walls, 
probably because they are formed very close to the moist soil. The cortex 
is composed of four to seven rows of cells. The vascular bundle is small, 
