502 Uphof. — - Contributions towards a Knowledge of 
cells which are thin-walled, and which the author considers to have origi- 
nated from the epidermic cells, as when very young these cells lie in radial 
direction towards one another. Sometimes it happens that the epidermis 
of such a root has formed a few root-hairs ; but after having penetrated the 
soil the root-hairs are abundantly formed, not, however, from every epidermic 
cell, e. g. in the case of S. lepidophylla or S. pilifera. 
Fig. V. i, 2, S. Bakeriana : i, part of young rhizophore ; 2, old rhizophore. 3-7, S. Martensi ; 
3, rhizophore surrounded by air; 4, rhizophore approaching the soil; 5, rhizophore touching the 
soil, showing habit of aerial root and terrestrial root ; 6, 7, root developed in the soil. 
Anatomically and physiologically interesting was the following experi- 
ment. Growing rhizophores, which were 3 to 10 millimetres distant from 
the soil, were covered lengthwise for one half with wet soil, the other side 
being exposed to the air ; after ten days the latter part had a construction 
like a root developed in the air, while that part which was grown against 
the soil had the same appearance as a terrestrial root, e. g. thin epidermis 
