162 Sargant and Arber .— The Comparative Morphology of 
history have been traced in the vascular system of seedlings belonging 
to other monocotyledonous families, to Dicotyledons, and to Gymno- 
sperms. 1 The Grasses, however, have been neglected of late years, and we 
felt it desirable to repeat and extend Van Tieghem’s observations on them 
with improved methods, and in the light of wider experience. This task 
we began together at Reigate in 1902, but owing to various interruptions 
it has only just been finished. 
We wish to express our thanks here to Miss E. N. Thomas, D.Sc., for 
permission to use her preparations, notes, and drawings of the Zingiberaceae 
(see p. 209) ; to Mrs. G. R. Taylor for the loan of her preparations from 
Triticum and Hordeum ; to Dr. O. Stapf, F.R.S., for various suggestions 
and criticisms ; and to Mr. R. I. Lynch, M.A., of the Botanic Garden, 
Cambridge, for the gift of seeds and other material. 
Besides the various types of Grasses, we have examined seedlings from 
other monocotyledonous families, choosing those in which the cotyledonary 
sheath is a prominent feature; and we have continued a detailed study of 
certain seedlings belonging to the Zingiberaceae which had been begun by 
Miss Thomas in the laboratory at Reigate. Her observations on the 
course of the bundles in the cotyledonary sheath of Elettaria suggested 
to us an explanation of the vascular skeleton in the coleoptile of Arena , 
which has been confirmed by further research. We think that the vascular 
symmetry of the seedling in this genus approaches that of the Arena type 
in the Gramineae, and gives a clue to the homologies of seedlings included 
in the other types. 
Many of the conclusions which we draw from these studies are identical 
with those of Van Tieghem in 1872, of Schlickum in 1896, and others. 
We take a new view of the morphological nature of the mesocotyl, and this 
is perhaps the chief contribution which we make to the theory of the subject. 
The mass of evidence examined is considerable, and much of it is new. 
We divide it under two heads; first the description of certain seedling 
types among the Grasses themselves, and then that of a few selected species 
1 See Sargant, E., Presidential Address, Section K, Botany, Brit. Assn. Report, Birmingham, 
1913. On pp. 703 and 704 will be found a list of references to papers dealing with the seedlings of 
Angiosperms and Gymnosperms from an anatomical standpoint. The following additional references 
may be added to this list: 
Hill, T. G., and de Fraine, E. : A Consideration of the Facts relating to the Structure of 
Seedlings. Ann. of Bot., vol. xxvii, pp. 257-72, four text-figs., 1913. 
Hill, T. G., and de Fraine, E. : On the Classification of Seed-Leaves. Ann. of Bot., vol. xxviii, 
pp. 359-62, 1914. 
Lee, E.: Observations on the Seedling Anatomy of certain Sympetalae. II. Compositae. 
Ann. of Bot., vol. xxviii, pp. 303-29, thirteen text-figs., 1914. 
Mellor, A. E. : The Seedling Structure of Dryas octopetala . The Naturalist, 1911, pp. 310-12, 
six text-figs. 
Thomas, E. N.: Seedling Anatomy of Ranales, Rhoeadales, and Rosales. Ann. of Bot., 
vol. xxviii, pp. 695-733, two plates, forty-three text-figs., 1914. 
