Apical Meristems of the Roots of Monocotyledons. 119 
I am indebted to Mr. L. A. Boodle for the photographs repro- 
ducee in Figs. 24 and 25. 
1 he Figures on Plate VIII. are from my own drawings. 
DESCRIPTION OF FIGURES ON PLATE VIII., ILLUSTRATING 
MRS. D. H. SCOTT’S PAPER “ON THE MEGASPORE OF 
L E PID O ST ROB US FOLIA CE US." 
Drawings of megaspores of Lepirfostrobus foliaccns, showing the appendage. 
The numbers are those of the slides in Dr. Scott’s collection. 1490 
shows a megaspore in a sporangium. 5 is represented in the photograph 
Fig. 25. 1217 is represented in the photograph Fig. 24. 
THE APICAL MERISTEMS OF THE ROOTS OF 
CERTAIN AQUATIC MONOCOTYLEDONS, 
By Daisy G. Scott, B.Sc. 
(University of Liverpool). 
[Plate IX.] 
mHE mode of origin of the permanent tissues from the apical 
| meristem in the root of the Monocotyledon has been the 
subject of investigation at the hands of many anatomists. The 
results arrived at have been summarised more especially by two 
authorities, viz. : by De Bary in his “ Vergleichende Anatomie 
der Vegetationsorgane der Phanerogamen und Farnen,” 1877, 
(English Edition, 1884), and by Van Tieghem in “ L’origine des 
membres endogenes,” 1889. These views may be expressed briefly 
as follows :— 
De Bary considers that there are two types of structure in the 
apices of the roots of Monocotyledons: (a), a type found in very 
few Monocotyledons, in which there are four initial layers giving 
rise respectively to (1) the plerome, (2) the perihlem, (3) the der. 
matogen, and (4) the calyptrogen and (6), a type found in the 
majority of Monocotyledons, in which there are three sets of 
initials giving rise respectively to (1) the plerome, (2) the perihlem 
and dermatogen together, (3) the calyptrogen. De Bary further 
holds that the epidermis is always a single layer, and that this 
layer originates separately or from a common group with the 
perihlem. 
Van Tieghem, with but few exceptions, considers that the mode 
