62 
Pond . — 77 a ? Incapacity of the 
it is well known that the latter contains enzyme. Some have based con- 
clusions on the fact that the ‘ culture fluid ’ reduced Fehling’s solution. 
The latter is of no significance unless it be known that reducing substances 
are not already present in the endosperm. 
It is of course essential to understand what constitutes auto-depletion. 
The mere diffusion of soluble cell-substance from the tissue cannot be 
regarded as such. There must be evidence of chemical change, such as 
corrosion of starch-grains or dissolution of cell-wall. That the storage 
organs in some seeds are the cotyledons must not be overlooked, and the 
distinction must always be made between the behaviour of fleshy embryos 
and endosperms. 
Historical. 
Gris (’ 64 , p. 90), in a notable contribution to the anatomy and 
physiology of germination, mentions some changes which were observed in 
the cell contents (aleurone especially) during germination, but Van Tieghem 
was the first to attack the problem directly. Van Tieghem ( 77 , p. 582) 
found that isolated endosperms of Ricinits communis under germination 
respire and are self-digesting, since the aleurone and oil are consumed, 
while the endosperms of Canna (amylaceous) and date (horny) are ‘ passive * 
and remain unchanged. He clearly implies that endosperms rich in oil 
and aleurone are self-digesting and possess vitality, while starchy endo- 
sperms and those containing reserve cellulose are not self-digesting and 
do not possess vitality. This conclusion rests purely on microscopical 
observations, and while the changes observed in Ricinus do indicate self- 
digestion, the possibility of a feeble digestion by the date is not excluded 
by such observations. So far as I am aware, this conclusion of Van 
Tieghem’s regarding Ricinus has never been questioned. 
Green (’ 90 , p. 146) investigated the germination of Ricinus communis 
and found a ‘ ferment to exist as zymogen in the resting seed which is 
readily developed by warmth and weak acids into an active condition.’ 
As to the relative influence of the endosperm and embryo he found ‘ the 
changes to be initiated in the endosperm, for they take place, although 
more slowly when the embryo is carefully removed/ The changes referred 
to consist (Green, ’ 90 , p. 147) in the saponification of fat into glycerine and 
ricinoleic acid especially, also the formation of sugar. Unfortunately the 
details of this work are not sufficient to permit any judgement as to the 
degree of demonstration attained. 
Green (’86, p. 57) made glycerine extracts of the cotyledons of date- 
seedlings and of the endosperm-residue. Both extracts were applied to 
ground endosperms of resting date-seeds, but neither gave evidence of 
hydrolytic activity. We do not know what evidence was searched for, as 
the author merely states that, ‘after prolonged action neither of them 
