64 BOTANICAL GAZETTE [yoy 
In the heterotypic mitosis STRASBURGER interprets the double condition asa 
parallel conjugation and not as an early splitting, and in this parallel conjugation 
he finds the explanation of the reduction from the 2x to the x number of chrome 
somes. Galtonia candicans furnishes particularly strong evidence that there isa 
pairing rather than a splitting. 
STRASBURGER was one of the first to claim that the nucleus is the physical 
basis of heredity. Since it has been urged that other structures are concerned, the 
sperm nuclei of Lilium were carefully reexamined, and it was found that only the 
nucleus, with no trace of cytoplasm from the pollen tube, enters the egg. 
The book closes with some interesting suggestions in regard to the origin ant 
development of the nucleus: The original protoplasm had no nuclei, all its pars 
ing capable of both formative and nutritive functions. Then there wasa grad- 
ual separation of formative and nutritive parts, and the formative parts were the 
first differentiated carriers of hereditary qualities. At first they were scattered? 
e cytoplasm, but later became grouped, as in the Cyanophyceae. Next the 
nucleus would be marked off from the cytoplasm by a membrane. Simple co 
striction might suffice for the division of such a nucleus, but as the different 
between hereditary units became so great that each unit carried only one quality 
a more exact division would become necessary. The units would become arrange! 
longitudinally in a thread, where they would undergo a doubling, and the long 
tudinal division of the thread would separate the product of that doubling. The 
complete resemblance between the mitoses of higher plants and animals makes 
this sequence very probable. - 
The book touches upon almost every phase of cytological investigation al 
consequently only a few of its more important features can be mentioned in# 
review.—CHARLES J. CHAMBERLAIN. a 
Biology of chlorophyll 
Starting from the complementary colors of marine algae, an accepted adap 
tion to the light at varying depths, as suggested by ENGLEMANN (1883), and th 
complementary tints attained promptly by certain Oscillatoriae, when exposed # 
light of differing hues, as shown by GarpuKow (1902), STAHL proposes to inquit 
why plants are green and not some other color, and whether the green of land a 
water plants is not an adaptation to the composition of sunlight, modified by’ 
passage through the atmosphere. Citing the results of physical investigations | 
show that in diffuse light the blue and violet rays prevail, and in direct * 
light the red and yellow, he claims that an unrecognized relation exists betwet 
these facts and the selective absorption of the chlorophyll. The yellow compos 
serves to absorb the blue-violet; the green component the red-yellow. The 
pigment is complementary to the blue of the sky, and the green to the red-ye° 
rays which pass through an atmosphere whose haziness becomes evident toe 
Ss Stant, Ernst, Zur Biologie des Chlorophylls: Laubfarbe und Himmelsid 
Vergilbung und Etiolement. 8vo. pp. vit154. pl. 1. Jena: Gustav Fischer. % 
M 4. a 
