492 
starch degradable to maltose, which forms the bulk of 
the granule, amylocellulose or amylopectin, and a 
small proportion of carbohydrate, possibly crystalline, 
soluble in cold water. It is probable that these are 
present in different proportions in the various starches, 
and so give rise to such differences as Reichert has 
observed. 
Some valuable observations on the characters of 
hard and tender barleys, published H. C. A. Vine in 
the Journal of the Institute of Brewing, may be men- 
tioned in this connection. A barley corn may contain 
starch granules of all sizes, the variation being due 
to the conditions under which it develops. Mal- 
nutrition of barley leads to a high ratio of small 
starch granules which are more resistant to enzyme 
action, to moisture, and to heat than the normal 
mature granules. Those granules which have the 
more favourable position in the enclosing cell are 
able to appropriate a large proportion of the nutriment 
supplied by the protoplasm, and so become normal 
large starch granules, each consisting of many layers 
containing much granulose, tender and readily acted 
upon. 
Similar observations were made by the writer some 
years back when it was pointed out that there is 
considerable variation in the proportion of large to 
small granules in wheat starch. Those types of flour 
which are the best for certain purposes contain the 
greatest proportion of large granules, the property 
being quite characteristic. 
Hence it would seem that, over and above species 
variation, differences due to environment and nurture 
may appear in the starches, and it is possible that 
the further study of such a substance as starch may 
provide material for the solution of many vexed 
problems. 
In addition to the detailed account of the tests 
applied to each starch, which are recorded also in 
the form of a curve which is shown to be character- 
istic for each individual, Prof. Reichert includes in 
his book a beautiful series of photomicrographs taken 
in ordinary and polarised light. These enhance very 
materially the value of the work, although they must 
have increased greatly the cost of publication. The 
author has further been at pains to. summarise at 
some length previous work on starch, both on the 
chemical and on the botanical side. His account is a 
valuable one if only.as showing how much uncertainty 
exists at present in the knowledge of starch and its 
transformations. HD. oye 
TRANSPIRATION IN PLANTS. 
ewe paper by Sir Francis Darwin (Proceedings 
of the Royal Society, B, vol. Ixxxvii.) mark an 
important advance in the study of the process of trans- 
piration in plants. Hitherto, although transpiration 
is perhaps more directly under the rule of external 
physical conditions than any other physiological func- 
tion of plants, there has been no complete experimental 
demonstration of the relation ‘between the loss of 
water-vapour from leaves and the relative humidity of 
the air or of the effect on transpiration of variation 
in the illumination to which the leaf is subjected. 
These lacunz are due to the fact that transpiration 
depends largely on the opening and closing of the 
stomata, the aperture of which varies in area with 
varying external conditions. To eliminate from the 
problem the varying stomatal aperture, the author 
blocks the stomata by smearing the leaf with cocoa- 
fat or vaseline, and then makes incisions which place 
the intercellular spaces in communication with the 
atmosphere; by measuring the thickness of the leaf 
and making incisions of a certain total length, the 
NO, 2232, Wil Gal 
NATURE © 
[Jury 9, 1914 \ 
area thus exposed is made to correspond with the area 
of the stomatal apertures under ordinary conditions. 
By using this ingenious method, the author finds that 
the line joining the abscissze representing the trans- — 
piration for different degrees of atmospheric humidity 
is practically straight, but that the transpiration begins 
at about 5 per cent. above saturation, and from calcu- 
lation of the vapour pressures at saturation and this 
degree of supersaturation, it appears that the internal — 
temperature of the leaf which can distil off vapour in 
saturated air is about 1° C. above that of the air, this 
increased temperature being attributable to respira- 
tion. 
The second paper gives the results obtained by 
applying this method to the investigation of the effect 
of light on transpiration. In April the transpiration 
of ivy was the same in diffused daylight and in dark- 
ness, while a month later the transpiration in light 
was double that in darkness, but the average ratio for 
transpiration in light and darkness was 135 : 100, 
though between May 14 and June 16 the laurel gave 
an average 150: 100, The cause of the increased 
reaction fo illumination in early summer as compared 
with spring is not completely explained, the author 
having no evidence as to whether the increased per- 
meability of the leaves to water is a periodic effect, or 
connected with the age of the leaf, or with the bright- 
ness of the summer sky, as compared with illumina- 
tion earlier in the year. 
THE AMERICAN PHILOSOPHICAL 
SOCIETY. 
a te annual general meeting of the American 
Philosophical Society was held in Philadelphia 
on April 23-25 inclusive, when numerous papers em- 
bodying the results of original researches were read. 
It is possible here to refer only to the more important 
and to those of wide scientific interest. 
The president, Dr. William W. Keen, was in the 
chair at the opening meeting, and among the papers 
presented was one on the segregation of ‘‘unit 
characters”’ in the zygote of GEnothera with twin and 
triplet hybrids in the first generation, by Prof. G. F. 
Atkinson, Cornell University. The segregation of 
several distinct hybrid types in the first generation 
of a cross between two species is a rare phenomenon. 
In Prof. Atkinson’s experimental studies, the two 
parents are Ctnothera nutans and CE. pycnocarpa, wild 
species of the evening primrose in the vicinity of 
Ithaca, N.Y. They differ by more than thirty easily 
recognisable contrast pairs of ‘‘unit characters,”’ or, 
in terms of the ‘‘presence and absence’’ hypothesis, 
there are more than sixty ‘‘factors’’ or recognisable 
characters which meet in the fertilised egg of the 
cross between the two parents. These characters 
relate to the habit and colour of the adults, features © 
of the rosettes, foliage, and inflorescence. When 
pycnocarpa is the mother, two distinct hybrid types — 
are segregated in the first generation, and have been 
brought to maturity. These are ‘‘twin hybrids.” 
When nutans is the mother, the same twin hybrids 
appear, and, in addition, a triplet which at present is 
in the rosette stage. 
The analysis of the hybrids shows a distinct linking 
or association of certain characters. Examples of this 
linking of characters are as follows :—First, habit 
characters; secondly, colour characters; thirdly, petal 
characters; fourthly, broadness and toothedness of 
rosette leaves; fifthly, narrowness and cutness of 
rosette leaves; sixthly, crinkledness, convexity, and 
red-veinedness of rosette leaves; seventhly, plainness, 
furrowedness, and white-veinedness of rosette leaves. 
The following hypotheses are considered :—(1) De 
