OcTOBER 23, 1913] 
probably others here besides myself who have reason 
to be grateful to him for that charming introduction 
to field botany, and for the companion volume on 
“Flowers, Fruits, and Leaves.” The great mass of 
first-hand information on the external characters of 
seedlings, contained in two massive volumes under the 
modest title of ‘‘A Contribution to our Knowledge of 
Seedlings,” was collected under his direction and put 
together by himself. It is not only a book of refer- 
ence to students of vegetable embryology, but no doubt 
played its part in reviving interest in that important 
subject. The work which he published was, however, 
the least part of Lord Avebury’s contribution to 
natural history. He represented a small but most 
distinguished class of naturalists, amateurs in the best 
sense of the word, since they work for pure love 
of the subject. Whether they happen to be men of 
affairs in great positions, like Lord Avebury, or 
artisans devoting their Saturday afternoons to original 
research in natural history, they are the salt of the 
subject, preserving it from the worst effects of a purely 
professional and academic standard. 
There is one more event of the past year to be 
mentioned before entering on the professional portion 
of this address. Section K has made a great innova- 
tion in choosing a woman for its president this year, 
and I will not refrain from thanking you in the name 
of my sex because I happen to be the woman chosen. 
And though I must and do feel very keenly the honour 
you have done me as a botanist in electing me to this 
position, yet that feeling is less prominent than grati- 
tude for the generosity shown to all women in that 
choice. Speaking in their name, I may venture to say 
that the highest form of generosity is that which 
dares to do an act of justice in the face of custom 
and prejudice. 
The main subject of my address this morning is the 
development of botanical embryology since 1870. 
Botanists, as well as zoologists, have used the term 
embryology in two senses. Balfour’s remarks apply 
to both sciences :— 
“Strictly interpreted according to the meaning of 
the word, it ought to deal with the growth and 
structure of organisms during their development 
within the egg-membranes, before they are capable 
of leading an independent existence. Modern in- 
vestigators have, however, shown that such a limita- 
tion of science would have a purely artificial char- 
acter, and the term embryology is now employed to 
cover the anatomy and physiology of the organism 
during the whole period included between its first 
coming into being and its attainment of the adult 
state.”” 
The older botanists used the term in the narrower 
sense. They included the study of the embryo-sac 
and the structures contained in it before the forma- 
tion of the unfertilised egg-cell, as well as the fer- 
tilisation of the latter and its subsequent divisions. 
But they did not proceed beyond the resting-stage of 
the embryo within the ripe seed. Here, as in 
zoology, this division is arbitrary and inconvenient. 
Accordingly, in the following remarks on the em- 
bryology of Angiosperms, I include every stage in 
the development of the plant, from the first division 
of the fertilised egg-cell to maturity. 
Systematists, from Czesalpino onwards, have paid 
much attention to the structure of the seed, and their 
observations are the earliest we possess on botanical 
embryology. They were, indeed, forced to study the 
embryo because its characters are often of systematic 
importance. The number of cotyledons, for instance, 
is the most constant character which separates the 
two great classes of Angiosperms. Again, the endo- 
sperm is not part of the embryo, but its presence or 
NO. 2295, VOL. 92] 
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NATURE 
243 
absence in the ripe seed—so important systematically 
—determines the functions of the cotyledons after 
germination, and thus influences their structure pro- 
foundly. In this way botanists became familiar with 
the structure of the embryo in the ripe seed before 
they had traced its origin from the fertilised egg-cell 
or followed its development after germination, 
The early history of the embryo was a sealed book 
to observers without the help of the compound micro- 
scope. Accordingly we find that work on the external 
morphology of seedlings preceded that on the forma- 
tion of an embryo. For the description of seedlings 
we must go back to the middle of last century. The 
greatest name in this school is that of Thilo Irmisch 
(1815-79). His work, like that of earlier observers 
in the same field, was neglected by the succeeding 
generation owing to the rapid development of micro- 
scopic botany. For a time the study of anatomy 
eclipsed that of external morphology. 
The earliest observers to study the embryo-sac of 
Angiosperms with the help of the compound micro- 
scope were naturally attracted by the history of the 
ovum and the process of fertilisation. Little pro- 
gress was made in this direction, however, owing to 
the imperfect technique of the day. The divisions 
of the fertilised egg-cell are more easily followed, as 
Hanstein showed in 1870. His classical paper is the 
foundation of botanical embryology in the narrower 
sense—that is, of the study of the embryo from origin 
to germination. 
This period in the plant’s history would seem, 
indeed, very well defined. It begins with the first 
division of the fertilised egg-cell—undoubtedly a 
natural epoch, for a new generation dates from it. 
It ends with the formation of the ripe seed, which is 
a true physiological epoch, since it corresponds with a 
complete change in the conditions of life. We have 
seen also that the morphologists who have dealt with 
the immature plant have fallen naturally into two 
groups, one ending and the other beginning their 
work at this very point. 
Experience, however, has shown here, as in zoology, 
that embryologists lose more than they gain by this 
division of their subject. It is, indeed, neither so 
simple nor so natural as it appears at first sight. 
It is not simple because the embryo is not always 
completely dormant during the interval between the 
formation of the ripe seed. and the first steps in ger- 
mination. On the contrary, in a large proportion of 
Monocotyledons, and in a smaller but still consider- 
able proportion of Dicotyledons, the embryo is an 
almost undifferentiated mass of meristem when the 
seed first ripens. It becomes differentiated internally 
and externally by degrees during the long interval 
before germination. This is sometimes called the 
maturation of the seed, and it is quite distinct from 
its ripening. Maturation is a process characteristic 
of the seeds of geophilous plants, which commonly 
lie in the ground for a year at least before germina- 
tion. 
In such cases the period of rest occurs immediately 
after the seed is ripe, and while the embryo is still 
undifferentiated. But the embryo is not comparable 
morphologically to that in the seed of an annual, 
for example, which may have ripened at the same time. 
The embryo of an annual has root, stem, and leaves, 
besides its cotyledons, and is ready to germinate 
immediately on the return of spring. 
The morphologist, then, must continue the study 
of his geophilous embryo throughout the period of 
maturation if he is to compare it with that of the 
annual. Even then he will find it less advanced than 
the annual embryo, though both be examined as they 
break out of the seed. For the geophyte may perhaps 
