the Anatomy of the Genus Selaginella . 51 1 
Selaginella forniosa . 
The aerial roots have a length of 40 to 60 millimetres and a diameter of 
| to | millimetre. The epidermis is relatively large-celled, also the 
hypodermis. The cuticle is well pronounced ; the cells of the hypodermis 
are not as thick as is the case with other species. The cells of the cortex 
are composed of seven to eight rows of cells and are larger than those of the 
hypodermis. The endodermis, as a rule, can be well distinguished from the 
other tissues. The xylem possesses eight tracheides in the protoxylem and 
five to eight tracheides in the metaxylem. 
The terrestrial roots show, with the exception of the first three cell- 
layers, the same anatomical construction as that of the rhizophore ; although 
the cortex is not composed of as many layers of cells, the hypodermis on the 
other hand remains the same. The vascular bundle is almost the same : 
there are only a few tracheides less. 
Selaginella aptis . 
The rhizophore is very thin and fibre-like ; its length amounts to 5 
to 12 millimetres and its diameter J to J millimetre. The cells of the 
