228 BOTANICAL GAZETTE [MARCHE 
Opuntia forms the columnar Cereus line was derived, with its numerous 
generic branches and diverse habits. Low down upon the columnar Cereus 
line the Echinocactus line branched out, which gave rise later to Mamillaria, 
and still later to Anhalonium. — J. M. C. - 
A REDUCTION DIVISION of the chromosomes (in Weissmann’s sense) is 
supposed by most botanists not to occur in plants. Guignard, Strasburger,” 
Sargant, Mottier, and many others find a longitudinal division of the chromo- 
somes, and, consequently, only a numerical reduction. Schaffner finds a 
transverse division, and, consequently, a qualitative division (reduction divi- 
sion) in the first division in the embryo-sac of Zi/ium,; Belajeff believes that 
a reduction division takes place in the second division of pollen mother cells; 
Calkins finds a reduction division in the second division of the spore mother 
cells of ferns. 
A recent paper by W.C. Stevens” deals with the chromosome problem i 
ferns. Scolopendrium vulgare, Cystopteris Sragilis and Pteris aguilina wert 
investigated. The writer’s summary is about as follows: In the first division 
of the spore mother cell the spirem thread splits longitudinally and then seg- 
ments into one half the usual number of chromosomes. e dau ghter chro- 
mosomes are short and thick, and in their form resemble tetrads, but there is 
no transverse division. The daughter chromosomes begin to separate some- 
times at the ends and sometimes in the middle, thus forming double rods oF 
ring-shaped chromosomes. In the daughter nuclei the chromosomes unite 
into a single nuclear thread. In the second division this thread splits longi- 
tudinally and segments transversely, as in the first division. It follows that 
there is merely a reduction in the number of chromosomes, and not a reduction 
division. Calkins’s figures lack i important stages and do not prove 4 reduction 
division. A thorough search failed to reveal centrosomes or multipolar spin- 
les. —CHARLES J. CHAMBERLAIN. 
FORESTRY IN MINNESOTA, by Professor Samuel B. Green, published by 
the Minnesota Forestry Association, has been recently issued. It pies 
bound and well illustrated, and contains a good glossary and index, $# 
details that greatly enhance the value of a most useful book. Prof 
Green has here brought together his class lectures, and they show him ae 
a thoroughly practical instructor. The little book contains just a of 
intending planter and the forest land owner need to know. The ihe bs 
tree growth is sketched, but the book is full of good practical suggestions 
er-cells, 
* Strasburger and Mottier reported a transverse division in pollen mt 
but almost immediately acknowledged that their conclusion needed revisio 
898. 
Gaz. 26: 220-221. 1 deutsch : 
d. oe 
ih 
™ Ueber Chromosomentheilung bei der Sporenbildung der Farne. Ber. 
1808. 
bot. Gesell. 16: 261-265. 1 
