279 
The Origin of Triple Fusion. 
evidence is against the upper ranges of illumination being sought 
by plants for the purpose of increased assimilation. The duration 
of illumination might well on the other hand be in direct relation 
to the accumulating amount of assimilated products; but these 
considerations, worked out in the laboratory, have yet to be trans¬ 
ferred to purely natural conditions. It may well be that the lower 
limit of light-range is determined by assimilation and the upper by 
some quite different cause. 
The significance of Lichtgenuss still awaits fundamental inves¬ 
tigation, but to Wiesner we are indebted for a very precise and 
full knowledge of the relations that hold in Nature. 
F. F. B. 
THE ORIGIN OF TRIPLE FUSION 
A Suggestion. 
Bv Emily M. Berridge, B.Sc. 
[Text-Fig. 17 ]. 
HE problem of the origin of the Angiospermic endosperm, 
which, after the discovery of double fertilization and of the 
unique process of triple fusion, seemed to become more intricate 
and more difficult of solution than ever before, has recently been 
attracting a considerable amount of attention. 
Within the last year two papers have appeared dealing with 
the question, both authors basing their views mainly on recent 
work carried out by American botanists on the embryogeny of the 
Gymnosperms, while a third suggestion has been brought forward by 
Dr. Land in his paper on Ephedra trifurca. 
Dr. Land (1) describes a peculiar process of tissue-formation 
within the upper part of the archegonium of this plant, which he 
regards as the precursor to endosperm development among the 
Angiosperms. This curious tissue also occurs in Ephedra distacliya 
about the time of the commencement of pro-embryo formation, and 
arises in exactly the same way; first a fibrillar structure appears in 
the cytoplasm, linking together the free fragments of chromatin 
material introdued by the proteid vacuoles, and then each fragment 
surrounds itself with a tiny zone of cytoplasm and a delicate cell 
