128 Apical Meristems of the Roots of Monocotyledons. 
are necessary to enable the outer layers to expand sufficiently to 
enclose the increased number of inner layers. 
My results appear to support the views held by De Bary, 
inasmuch as they seem to shew that the roots of the aquatic 
Monocotyledons studied are developed in the same way as are, 
according to De Bary, the majority of the roots in that group, 
that is, from three sets of initials giving rise respectively to (i.) the 
calyptrogen, (ii.) the periblem and dermatogen together, (iii.) the 
plerome. 
LITERATURE. 
1. Dc Bary. “ Vergleichcnde Anatomic, &c.,” 1877. Eng. Ed. 1889. 
2. Van Tieghem. “ L’origine des membres endogenes.” 1889. 
3. Janczewski. Ann. Sci. Nat. 5 ser. tom. XX. 
4. Treub. “ Le Mdristeme primitif de la racine dans les Monocotyledoncs.” 
Leiden 1876. 
5. Buscalioni. Sull’ anatomia del cilindro centralc nellc radici della 
Monocotiledoni. Malpighia XV. (1902). 
6. Pirotta. Origine e differenziazione degli elementi vascolari primaro nclli 
radici della Monocotyledoni. Rendic. Acad. Lincei, ser 5 XI. (1902). 
7. Hanstein. “ Die Scheitelzellgruppe im Vegetationspunkt der 
Phanerogamen.” Bonn 1868. 
8. Holle. Bot. Ztg. 1876 and 1877. 
9. Eriksson. Bot. Ztg. 1876. 
10. Flahault. Ann. Sci. Nat. ser. 6, tom 11. 
11. Schwendener. “ Scheitelwachstum der Phanerogamcnwurzeln. K. Acad. 
Wiss. Berlin, 1882, and Bot. Ztg. 1882. 
DESCRIPTION OF FIGURES ON PLATE IX. 
Fig. 1. 
Alisma. 
Fig. 2. 
Alisma. 
Fig. 3. 
Alisma. 
Fig. 4. 
A lisma. 
Fig. 5. 
Bntomus. 
Fig. 6. 
Butomus. 
Fig. 7. 
Vallisneria. 
Fig. 8. 
Vallisneria. 
Fig. 9. 
Vallisneria. 
Fig. 10. 
Ruppia. 
Fig. 11. 
Nnias. 
Fig. 12. 
Zostera. 
Fig. 13. 
Zoster a. 
Fig. 14. 
Stratiotes. 
A longitudinal section through the apex of a young root. 
A longitudinal section through the apex of an older 
root. 
A transverse section through a root at some dislance 
from the apex. 
A transverse section through a fairly old root. 
A longitudinal section through the apex of a young 
root. 
A longitudinal section through a somewhat older root. 
A longitudinal section through a young root. 
A longitudinal section through an older root. 
A transverse section through a root a short distance 
from the apex. 
A longitudinal section through a young root. 
A longitudinal section through a young root. 
A longitudinal section through the apex. 
A transverse section through the root near the apex. 
A longitudinal section through the apex of a root. 
