i75 
1 he Meeting of the British Association. 
thoroughly dessicated over sulphuric acid could withstand tempera¬ 
tures varying according to the species from 90 "C. to 120 °C. for at 
least an hour. 
Miss Matthaei read an important paper on the Effect of 
Temperature on Carbon Dioxide Assimilation. The generally 
accepted view has long been that this function increases with rise 
of temperature from 0 °C to about 15 °C. and then remains unaffected 
by further rise, giving a curve which shews a sharp preliminary 
ascent and then a long, approximately flat top, as figured in Pfeffer’s 
“ Physiology of Plants.” Such a curve, though hitherto un¬ 
questioned, has no parallel in plant-physiology, and no clear 
rationale. Miss Matthaei’s researches prove that the true curve 
shews a steady continuous rise ; and thus assimilation is brought 
into line with other vital functions. The “ flat top ” is shewn to be 
due to experiments with insufficient illumination, the assimilation 
having been naturally unable to increase beyond the limit imposed 
by the inadequate amount ot radiant energy reaching the leaf. 
Miss Matthaei’s researches were carried out in Mr. F. F. Blackman’s 
laboratory at Cambridge. 
Of morphological papers one of the most interesting was 
Mr. J. C. Willis’, “ On the Dorsiventrality ot the Podostemaceae, with 
reference to Current Views on Evolution.” The author shewed that 
in this curious order—upon which he has extensive memoirs in 
preparation—a series of types can be traced shewing a gradual 
increase in dorsiventrality at first in the vegetative body alone, and 
then in the flower, finally extending to the embryo itself. This 
dorsiventrality of the flower is clearly not an adaptation to insect- 
visits, as is so often the case, since the more zygomorphic the 
flowers the more do they shew anemophily or autogamy. The 
most obvious view is that the increasing dorsiventrality of the 
plant-body has gradually forced itself upon the flower, which is more 
and more profoundly affected, without gaining any obvious advantage 
in the struggle for existence. This character of dorsiventrality in 
the flower and fruit is largely used in classifying the Podostemaceae 
into sub-orders and genera, but it is clear that if there is a progressive 
tendency to dorsiventrality in the plants belonging to this family, 
it may have taken effect in a similar manner and produced similar 
results in series of forms living in different parts of the world. 
Hence it seems likely that sub-orders, genera, and species may be 
polyphyletic, owing to this parallel or convergent evolution. Such 
a conclusion, of course, considerably affects our views on the relation 
of the geographical distribution of the family to its evolution. 
