1907] HOLM—RUBIACEAE 185 
in G. triflorum; the lack of collenchyma in H. coerulea and in the 
over-wintering leaves of H. purpurea; the presence of a water-storage 
tissue, amply represented in Cephalanthus, and only on the leptome 
side of the midrib and larger veins in Galium and Diodia; the endo- 
dermis-like parenchyma sheath in Galium. 
Some of these characters may not be constant. For instance, 
the relative development of the palisade tissue may be different, and 
it would be interesting to know the leaf-structure of Galium triflorum 
from northern Europe, and of the Japanese Mitchella. 
The family characters, as outlined by VESQUE and SOLEREDER, 
may be augmented, but hardly changed. The family is well repre- 
sented in North America, and an extended study of the southern 
and western species would no doubt give many interesting results. 
BROOKLAND, D. C. 
EXPLANATION OF PLATES VII-IX 
Cephalanthus occidentalis 
Fic. 1. Transverse section of root, showing development of cork; ef, epi- 
dermis; ex, exodermis; p, phellogen; c, outermost stratum of cortex. X 320. 
1G. 2. Epidermis of lower face of leaf with stomata. X240. 
Houstonia coerulea 
Fic. 3. Cross-section of stem leaf, showing a cell of epidermis with its cuticle 
from the upper face. X 240. 
Fic. 4. Epidermis from upper face of stem leaf with cuticular striations and 
stomata. 240. 
G. 5. Hair from leaf margin with spiral striations of cuticle. 240. 
as 1G. 6. Glandular hair from stipule. X240. 
Fic. 7. Epidermis with stomata from lower face of basal leaf. X 320. 
Houstonia purpurea 
Fic. 8. Hair from upper face of stem leaf. 240. 
Fic. 9. Epidermis with stomata from lower face of basal leaf. 240. 
Fic. 9A. Epidermis of upper face of basal leaf, showing cuticular striations 
and thickenings of the lateral cell walls. 320. 
Mitchella repens 
Fic. 10. Cells of epidermis from upper face of leaf, viewed en face. X 560. 
Fic. 11. Cross-section of leaf, showing epidermis (ep) and part of palisade 
tissue, (p). 560. 
Fic. 12. Epidermis of lower face of leaf, showing the stomata. X 320. 
Fic. 13. Epidermis of lower face of leaf. X 320. 
