512 Uphof. — Contributions towards a Knowledge of 
epidermis and hypodermis are very large, almost as large as those of the 
cortex cells. Cells of the epidermis and hypodermis only contain slightly 
secondary layers. The vascular bundle is small, although its elements are 
all represented; the xylem is only composed of five to six tracheides, of 
which two to three belong to the protoxylem. There is little difference in 
the construction of terrestrial roots. 
Selaginella Galeotii. 
The rhizophores attain a length of 80 to la o millimetres and a 
diameter of J to | millimetre. The epidermis cells are small ; those of the 
hypodermis are much larger and as big as those of the cortex. The cell- 
walls of epidermis are very thick ; very little space has been left in those of 
the older rhizophores. In many cells of the cortex a red pigment is 
developed in the vacuoles, or at least those which developed towards the 
side of the approaching light. The cortex is formed by twelve to twenty 
layers of cells. The vascular bundle, especially the xylem, is not as much 
developed as one would expect ; there are four to five tracheides in the 
protoxylem and about five in the metaxylem. The terrestrial root, which 
is much thinner than the aerial root, has a less developed cortex, which is 
formed by three to four layers of cells ; although otherwise it shows much 
the same development as the aerial root. 
Selaginella patnla. 
The aerial root reaches a length of io to 18 millimetres and a diameter 
of \ to -J millimetre. The cells of the epidermis, hypodermis, and cortex 
are practically of the same size ; only those of the inner cortex are larger. 
The cuticle is very little pronounced, although the other walls of the 
epidermis and those of the hypodermis are furnished with secondary layers. 
The vascular bundle does not differ much from that of .S. molliceps. The 
terrestrial root also does not show much difference, except that part which 
is directly in touch with the soil. 
Selaginella Martensi, 
The rhizophore becomes 30 to 60 millimetres in length and f to 1 milli- 
metre in diameter. The epidermis has a thick cuticle on plants which have 
been rather exposed, and as thin as an ordinary primary wall when 
developed in a shady and very moist environment. The other walls of the 
epidermis and those of the hypodermis are thickened in the same degree. 
The cortex is composed of twelve to fifteen usually thin-walled rows of 
cells. Towards the vascular bundle they become smaller. The endodermis 
and pericycle are very distinct. The elements of the phloem are well 
represented and hardly differ from those of a stem. The xylem is formed 
by four to five vessels of the protoxylem and ten to fourteen belonging to 
the metaxylem. 
