694 TRANSACTIONS OF SECTION K. 
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 germination. 
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. 
z ‘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 cut of the seed. For the geophyte may perhaps 
be four or five years before it flowers, while the annual has to complete its whole 
life-cycle in a single season. 
Nor is the division of the subject into two parts, the first ending with the 
embryo in the ripe seed, a natural one, even if the time of maturation be 
included in that first period. The structure of the embryo cannot be completely 
grasped by reference to its past only. The observer must expect adaptive 
characters of three kinds : first, those imposed upon the embryo in the past by 
its development within the embryo-sac while it is still parasitic on the parent 
plant; secondly, certain adaptations to the process of germination itself; and, 
finally, characters which will be useful after germination. Before the utility 
of the characters included in this third class can be fully understood, the 
development of the seedling must be followed for some time. In short, the 
structure of the embryo is dependent on its future, as well as on its past; and 
a division of the subject which excludes that future is, as Balfour says, purely 
artificial. Thus the work done of late years on the anatomy of the seedling has 
not only completed Irmisch’s work on its external morphology, but has also 
thrown light on the problems of early embryology attacked by Hanstein and 
his immediate followers. 
These problems are of two kinds, relating to the internal anatomy or the 
external morphology of the embryo. Hanstein himself was chiefly interested 
in the former. It is curious to realise when reading his paper that up to the 
date of its publication botanists were prepared to find an apical cell in the 
embryo of Angiosperms. They acknowledged, indeed, that no such cell existed 
in the growing-points of the mature plant.‘ There each new portion of tissue 
was formed by the activity of a group of similar and equivalent cells. But it 
still seemed possible that the embryo might possess an apical cell in the earlier 
stages of its growth—a reminiscence of its Cryptogamic ancestors. Hanstein’s 
work disposed once for all of this possibility. It was conclusive even against 
the great authority of Hofmeister, who had described an apical cell in the embryo 
of orchids. 
One general result of the work on the embryo since Hanstein’s time has been 
to discredit phylogenetic theories based on its early history. Indeed, it was 
hardly to be expected that a small mass of meristem, developing within a 
confined space and feeding parasitically on the tissues of the mother-plant, 
should preserve ancestral features, and one is surprised to find a morphologist 
with the experience and the wide grasp of Hanstein attaching so much import- 
ance to the succession of divisions within such a body. The conscientious 
student finds it a laborious task to follow the work done in plant embryology 
during the period which succeeded the publication of Hanstein’s great paper. 
No wonder that when the end is seen to discredit rather than crown much of 
that work, when he realises how little has been gained as a result of so much 
patient toil, he is apt to renounce the whole subject in disgust. Yet in Science 
we dare not rule out the unexpected, perhaps even Jess in morphology than 
elsewhere. Hanstein and his successors did good service when they described 
the growth of the pro-embryo from the fertilised egg-cell, its division into 
1 Korschelt in 1884 revived the hypothesis that the growing points of some 
Angiosperms at any rate increased by means of an apical cell. He worked 
chiefly on aquatic plants. His views have not been accepted. 
