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OcTOBER 23, 1913| 
NATURE 
249 
derived from an ancestor with one cotyledon, ap- 
parently terminal, which gave rise to the existing 
pair by a process of fission. But other interpretations 
were always possible, and the terminal hypothesis 
received a shock when Count Sohms-Laubach dis- 
covered that in certain Monocotyledons the single 
cotyledon is lateral from the first. _ 
‘Yhe comparative antiquity of Monocotyledons and 
Dicotyledons has been one of the first questions 
raised by the study of seedling anatomy. It is re- 
markable that both the hypotheses founded on work 
of this kind assert the greater antiquity of the 
dicotylous form. But if the cotyledonary member of 
Monocotyledons is derived from one or both cotyledons 
of an ancestral pair, it cannot be considered as ter- 
minal. Thus the evidence of seedling anatomy bids 
fair to settle both these questions, as | think it will 
settle others of the same kind mentioned by Hanstein. 
The descriptive work of Irmisch and the school he 
represents has been carried on of late years by an 
American naturalist, Mr. Theo. Holm, with all the 
technical advantages given by modern instruments of 
research. His papers are commonly written with 
systematic intention, but the external characters of 
the species he describes are correlated with their 
internal anatomy, and the structure of the adult 
form is traced from its origin in the seedling. His 
monograph on Podophyllum peltatum is an example 
of this method, and illustrates its advantages in a 
very striking way. But it is becoming much more 
usual to compare the seedling with the adult form, as 
may be seen in two monumental works now being 
published in parts: ‘‘Das Pflanzenreich,’’ edited by 
Engler, and ‘‘Lebensgeschichte der Bliitenpflanzen 
Mitteleuropas,”’ edited by Kirchner, Loew, and 
Schroter. 
In a very useful paper on modern developments of 
seedling anatomy Mr. Compton has pointed out that 
the subject has been attacked from several divergent 
points of view. I have already referred to the work 
of M. Chauveaud and Prof. Gravis, and have now 
come to that of a number of English botanists, whose 
aim—as Mr. Compton observes—is .mainly phylo- 
genetic. They are even more clearly distinguished 
by their methods, which are those of comparative 
anatomy. Instead of following the development of 
the seedling of a single species from germination to 
the age at which its cotyledons begin to decay, as 
M. Chauveaud has done in a number of carefully 
selected instances, they have compared the seedlings 
of different species and different genera at about the 
same age, generally choosing the epoch at which the 
tissues of cotyledon, hypocotyl, and primary root are 
most completely differentiated. There is nothing new 
in this treatment of the subject. It was employed in 
1872 by Prof. Van Tieghem’ in his paper on the 
anatomy of grass seedlings, in which he compares 
them with other Monocotyledons of the same age. 
Much greater precision is possible, however, now 
that the microtome has come into general use. 
The literature of this subject has increased rapidly 
of late years. The list of references in the footnote ™ 
10 Prof. Van Tieghem, Amn. Sec. Nat., ser. 5, xv., p. 
11 The following references are arranged ET a re 
Arber, A., The Cactacee ard the Study of Seedlings. Mew Piiyt., ix., 
P- 333) 1910. 
Compton, R. H., An Investigation of the Seedling Structure in Legumi- 
nose. Linn. Soc. Journ. Bot., xli., p. 1, 1912+ 
de Fraine, Ethel. The Seedling Structure of certain Cactaeca. Ann. Bot 
XxiV., P. 125, T9TO. ; 
Bt nae monology and Seedling Structure of Peperomia. Ann. 
Bot, Xxi., P. 395, 1906. 
Hill, T. G, oe Seedling Structure of certain Piferales. Ann. Bot. 
XX.) P. 160, 1906. f 
Hill, T. G., and de Fraine, Ethel. On the Seedling Structure of certain 
Centrosperma. Ann. Bot., xxvi.y p. 175, 1912. 
Hill, T. G., and de Fraine Fthel. On the !nfluence of the Structure of the 
Adult Plant upon the S-edling. New Piyt., xi., p. 319, 1912. 
Hill, T. G., and de Fraine, Ethel. A Consideration of the Facts 
NO. 2295, VOL. 92] 
appended to this paragraph is, I fear, far from 
complete. But it is not part of my plan to review 
this work critically. The time is, perhaps, not ripe 
for such a review, and certainly the time at my 
disposal to-day is quite insufficient for it. Perhaps | 
may be allowed to offer some general remarks, first 
on the method itself, and then on the criticisms it has 
encountered. 
To compare the structure of organisms with each 
other is, of course, the recognised method of compara- 
tive anatomy, of systematic botany, and, in fact, of all 
branches of morphology. The great difficulty in all 
such work is to distinguish between adaptive char- 
acters of comparatively recent origin and the char- 
acters inherited from remote ancestors. The history 
of systematic botany is very instructive in this respect. 
Systematists discovered by degrees, and by means of 
repeated failures, that characters could not be picked 
out as important for purposes of classification on 
a priori grounds. No character is of uniform import- 
ance throughout vascular plants, for example. On the 
contrary, it may be of great value in the classification 
of one group and worthless in another, though closely 
allied. Generations of botanists have laboured to build 
up the natural system in its present form, and it is 
constructed from the ruins of abandoned systems. 
We all agree now that the guiding principle in all 
morphology is that our classification should represent 
relationships founded on descent only. But the natural 
system was complete in its main features before that 
principle was understood. It represented the feeling 
for real affinity developed in botanists by the study 
of plant form, independently of any theory as to the 
cause of such affinity. 
This, of course, is the commonplace of botanical 
history, but we do not always realise that all morpho- 
logical work is done under similar conditions. The 
only valid appeal from criticism is to the future: a 
new method is approved by its results. Therefore, to 
embark on a new branch of morphology is a real 
adventure. The morphologist risks much time and 
much labour. He knows that the evidence which he 
proposes to gather painfully, to test critically, to pre- 
sent logically, may, after all, prove of little con- 
sequence, and he has to depend on his own instinct to 
lead him in the right course. In his degree he re- 
sembles Columbus, to whom a few sea-borne seeds 
and nuts meant a new continent. 
relating to the Structure Seedlings. Ann. Bot., XXViLL, p. 258 
1913. 
Lee, E. Observations on the Seedling Anatomy of certain Syfetalar 
Ann. Bot., XXvi., Pp. 727; 1912. 
Sargant, E. A New Typeof Transition from Stem to Root in the Vascular 
System of Seedlings. Ann. Bot,, xiv., p- 633, 1900. 
Sargant, E. The Origin of the Seed Leaf in Monocotyledons. New Phyt., 
i., Pp. 107, 1902. 
Sargant, E. A Theory of the Origin of Monocotyledons, founded on the 
Structure of their Seedlings. Amn. Bot., xvii., p- 1, 1903. 
Sargant, E. The Evolution of Monocotyledons. Bot. Gas., XXXVI, Pp. 
325, 1904. 
Smith, Winifred. The Anatomy of some Sapotaceous Seedlings. Trams. 
Linn. Soc., series 2. Bot. vii., p. 189, 1909. 
Tansley, A. G., and Thomas, fk. N- Root Structure in the Central 
Cylinder of the Hypocotyl. Mew P/yt. iil., p. 104, 1904- 
Tansley, A. G., and Thomas, E. N. The Phylegenetic Value of the 
Vascular Structure of Spermophytic Hypocotyls. Brit. Assoc. Report, 
1906. 
Thomas, E. N. A Theory of the Double Leaf Trace, founded on Seedling 
Structure. New PAyt., vi., p- 77, 1907- 
The references given above refer to Angiosperms only, but so much work 
of a similar nature has been done lately on Gymnospermous seedlings that 
I add a list of the pri: cipal papers :-— 
Dorety, Helen A. Vascular Anatomy of the Seedling of Microcycas 
calocoma. Bot. Gaz., x\vii., p. 139, 1909. 
Hill, T. G., and de Fraine, Ethel. The Seedling Structure of Gymno- 
sperm. I., Ann. Bot., xxii., p. 629. 1908. II., i. xxiil., p. 189, 1909. 
ILL, #d. xxiii., p. 433, 1909. 1V., 7a. xxiv., p. 319, 1910. 
Matte, H. L’appareil libéroligneux des Cycadies Caen, 1904. 
Shaw, F. J. F. The Seedling Structure of Avaucarra bidwillit. Ann. 
Bot., XXill., p- 321, 1909- 
Sykes, M. A. lhe Anatomy of Welwitschia mirabilis. .. + + 
Linn. Soc., 2. Bot. vii., p. 327, 1910. 
Thiessen, Reinhardt. The Vascular Anatomy of the Seedling of Dioon 
edule. Bot. Gaz., x\vi., p. 357, 1908- 
Trans. 
