the Anatomy of the Genus Selaginella. 517 
Some species form, when bruised, small stems instead of rhizophores ; 
these suggested to many investigators that the latter are leafless stems. 
The anatomy shows that these branches have the same construction as 
a stem and are positive heliotropic, whereas the so-called rhizophores have 
the construction of a root and are negative heliotropic. 
The vascular system is monarch ; the endodermis and pericycle are 
always present. The phloem shows the same arrangements as in the stem, 
although its elements are less abundant. The xylem is composed of one 
group of protoxylem and usually a well-developed metaxylem. 
The thick-walled tissue which follows the three layers of thin-walled 
cells of the periphery of the terrestrial roots apparently belongs to the 
hypodermis. 
Bibliography. 
1. Bower, F. O. : The Origin of a Land Flora. London, 1905. 
2. Bruchmann, H. : Von den Wurzeltragern der Selaginella Kraussiana. Flora, xcv. 150-66, 
1905. 
3. Campbell, D. H. : Structure and Development of Mosses and Ferns. New York, 1905. 
4. Engler and Prantl : Die natiirlichen Pflanzenfamilien, i. 621, 1900. # 
5. Fries, R. E. : Et Bidrag til kannedomen om .SV/^m^/fo-Rotbararna. Svensk bot. tidskr., v. 
252, 1912. 
6. Goebel, Karl : Organographie der Pflanzen, 2. Ausg. Jena, 1913. 
7. : Einleitung in die experimentelle Morphologie der Pflanzen. Leipzig, 1908. 
8. Nageli, C., and Leitgeb, H. : Entstehung und Wachstum der Wurzeln. Beitr. wiss. Bot., 
*pp. 73-160, 1868. 
9. Pfeffer, W. : Die Entwicklung des Keimes der Gattung Selaginella , Hanst. Abh. i. 1-80, 
1871. 
10. Sarauw, Geo. F. L. : Versuche liber die Verzweigungsbedingungen der Stutzwurzeln von 
Selaginella. Ber. der Deutschen Bot. Ges., ix. 51-65, 1891. 
11. Scott, D. H. : Studies in Fossil Botany. London, 1909. 
12. Tieghem, Ph. van : Traite botanique, 2 e ed. Paris, 1892. 
13. and Douliot : Reclierches comparatives sur l’origine des membres endo- 
genes dans les plantes vasculaires. Ann. d. sc. naturelles, Bot., vi.ii, 1888. 
14. Treub, M. : Recherches sur les organes de la vegetation de S. Mai'tensii. Museebot. de Leide, 
ii, 1877. 
15. Waage, Th. : Uber haubenlose Wurzeln der Hippocastanaceen und Sapindaceen. Ber. der 
Deutschen Bot. Ges., ix. 132-62, 1891. 
16. Warming, Eug. : Om Rodderne hos Neottia nidus avis. Videnskab. Medd. fra nat. Forening 
for 1877, PP- 26-32. 
17. Worsdell, W. C. : The Rhizophore of Selaginella; New Phytologist, ix, 1910. 
