348 
NATURE 
[June 4, 1914 
the book is a discussion of fertility and sterility 
in the light of recent advances. We have to 
thank Prof. Morgan for these lucid and scholarly 
lectures on heredity and sex, which express his 
characteristic combination of critical judgment and 
synthetic appreciation. The reader is assisted by 
the numerous illustrations, many of which are very 
fresh and interesting. fc: 
OUR BOOKSHEEF. 
Das Elisabeth Linné-Phdnomen  (sogenanntes 
Blitzen dey Bliiten) und seine Deutungen. By 
Proi dae.) Wee lhomas. “Pp. 953. Se ieuae 
G) Fischer, 1914.) Price. a 50 marics. 
Tuts small work has the two-fold object of direct- 
ing the attention of nature-lovers to the pleasing 
phenomenon of “Flashing Flowers,” which is 
more exactly defined as the Elizabeth Linnaeus 
Phenomenon, and of giving a scientific explana- 
tion of its cause. 
Perhaps the most interesting feature of the in- 
vestigation is the names with which it is asso- 
ciated, - beginning with Elizabeth Linnzus 
(daughter of the great Swedish botanist), who first 
observed the flashing of Indian Cress flowers at 
twilight in her father’s garden at Hammarby, 
near Uppsala, and published her observation with 
a comment from Linnzeus himself. Her discovery 
interested a number of scientific men, who 
ascribed the appearance to electricity, phosphor- 
escence, etc., or rejected it as imaginary and only 
visible to those who could see ghosts. High 
above them all stands Goethe, who answered 
Elizabeth Linnzeus’s pertinent question ‘‘ whether 
the flashing is in the flower or in the eye,” by 
referring to the effect upon the eye of brilliant 
complementary colours, and by pointing out that 
the flashing is only seen in a flower which comes 
sideways into the field of vision. 
Prof. Thomas gives an explanation of the 
phenomenon. It is perceived, he says, in twi- 
light, which makes red brighter and green duller 
than they appear in full daylight. As the image 
of the red flower moves from the peripheral part 
of the retina, where the rods are red-blind, to 
the fovea, the red is perceived somewhat more 
vividly than before, and this image coincides with 
the Purkinje after-image of the surroundings, 
giving the impression of a flash. How 
Die Wichtigsten Lagerstétten der “ Nichterze.” 
By Prof. O. Stutzer. Zweiter Teil: Kohle (All- 
gemeine Kohlengeologie). Pp. xvi+ 345 +xxix 
plates. (Berlin: Gebriider Borntraeger, 1914.) 
Price 16 marks. 
Tuts second part of Dr. Stutzer’s encyclopaedic 
work is entirely devoted to coal and other carbon- 
aceous deposits. The first, or petrographical, 
division of the volume deals with the chemical and 
physical characters of coal and the results of its 
microscopical examination, with a discussion of 
the theories of the origin of coal. The aim of the 
author is to bring together the observations and 
conclusions of all who have written upon the 
views of his own. The second division of the 
work is stratigraphical, and an immense amount 
of valuable information is collected and classified 
concerning coal-seams—their modes of occurrence 
and the indications which they exhibit of opera- 
tions taking place during and subsequently to 
their deposition. The third division of the book 
is statistical, dealing with coal-supply and coal- 
production in all parts of the globe, full use being 
made of the important work on ‘The Coal Re- 
sources of the World,” which was inaugurated at 
the meeting of the Geological Congress at Toronto 
and published last year. Throughout the work 
before us no effort seems to have been spared by 
its author in making the information complete and 
up-to-date. Among the numerous wood-cuts are 
given many graphic illustrations, which are of the 
greatest assistance to the reader, as well as copies 
of figures derived from the works of a great 
number of different authors. Taken altogether, 
this second part of Dr. Stutzer’s monograph fully 
realises the high expectations which must have 
been formed by all who have used his earlier 
volume. 
Descriptive Geometry. Part i., Lines and Planes. 
By Prof. John C. Tracey. Part ii., Solids. By 
Prot. H. B.. North, and’ Prot.J> Gx. foaeess 
Pp. x+126. (New York: John Wiley and 
Sons, Inc. ; London: Chapman and Hall, Ltd., 
7914.) Price 8s,.6d- eet. 
Peruars the most notable feature of this work is 
its logical development of the subject. Beginning 
with the point in space we are shown its plan, 
front elevation, and side elevation, when situated 
in the various positions relatively to the three 
planes of projection. Then follows an equally ex- 
haustive treatment of the line and plane. A very 
complete system of notation, specially suitable for 
oral instruction as well as for private reading, 
is carefully defined and strictly adhered to through- 
out. Also, in the authors’ scheme is a unique 
system of triple columns. In the first column the 
problem is stated in general terms along with the 
principles and previous problems involved. In the 
other two parallel columns we have an illustrative 
particular case, accompanied by a figure, or by a 
series of figures exhibiting the successive steps in 
the solution. The authors give special prominence 
to three fundamental constructions on which most 
of the subsequent work is based. 
A student who has thoroughly mastered the first 
part of the book should have little difficulty with 
the second, which deals with some of the simpler 
geometrical solids; their projections when situ- 
ated in easy and in difficult positions ; their sections 
by vertical, inclined, and oblique planes; the 
development and intersection of their surfaces ; and 
the determination of lines and planes tangential 
to them. 
The general treatment is purposely somewhat 
abstract, being unrelieved by practical problems 
or applications. The authors, however, propose 
to issue later a complete set of exercises for use 
with this verv thorough and sound work on 
subject, rather than to advocate any particular | descriptive geometry. 
NO.) 2327) Vile @3 || 
