146 BOTANICAL GAZETTE [FEBRUARY 
Reproduction of mildews. 
Harper has brought together the results of several years of study of 
nuclear activities in the mildews*in a lengthy and beautifully illustrated 
publication from the Carnegie Institution.2 It is impossible for us to consider 
more than the striking new features of his investigations. The paper contains 
a résumé of much of his earlier work and a broad discussion of many 
cytological principles which are of general interest and will richly repay the 
reader of this very creditable contribution to American botany. The author 
takes a strong stand for critical morphological analysis and classification of 
the stages in the life history of thallophytes, with a clear separation of phylo- 
anaes history from physiological functions. 
m mportant new features of HARpER’s research, chiefly in 
Phyllactinia, are @) the establishment of a “central body” within the nucleus, 
which constitutes a point of attachment for the chromatic elements and gives 
a clear polarity to the structure, and its continuous existence through the most 
important phases in the life history; (2) the evidence for the permanence of 
the chromosomes; and (3) the evidence that the triple mitoses preceded by 
synapsis in the ascus constitute a double reduction of the chromosomes which 
are quadrupled by the two nuclear fusions in the life history, the first fusion 
at the time of the sexual act and the second fusion within the young ascus. 
The central body is a permanent structure, always present in the resting 
nucleus, dividing with each mitosis, and the center for an arrangement of 
chromatic threads within the nucleus and for the attachment of spindle fibers 
during nuclear division. Its position determines a pole in the. nucleus around 
which are grouped the chromatic elements, which are thus always in connection 
with the central body, both in the resting nucleus and during mitosis. This 
e succession of mitoses in the life-history. HARPER has not been able to 
i the different sets of chromosomes after the nuclear fusions, for the 
chromatic elements and the central bodies unite very intimately. But the 
second fusion in the life history, that in the ascus, is followed at once by a 
period of synapsis and the triple mitoses out of which come the eight chromo- 
somes characteristic of the gametophytic phase of the form.—B. M. Davis. 
MINOR NOTICES. 
Observations in Spitzbergen——The flora of Spitzbergen is fairly known. 
Therefore, Dk. WuLFr, who accompanied the Swedish expedition for the measure- 
ment of an arc of the meridian, undertook to make ecological observations on 
the arctic plants,3 especially touching their transpiration, occurrence of mycorhiza 
2 HARPER, R. A., Sexual ee oe and the organization of the nucleus i 
certain mildews imp. 8vo. pp. . pls. 7. Washington: er Institution of 
apAbae gos. 
ULFF, THORILD, Observations botaniques faites au Spitzberg. Missions scien- 
ious pour a mesure d’un arc de méridien au Spitzberg. Mission uédoise. ‘Tome 
Il, X¢ section, Botanique. Traduit de Allemand par H. Marcet Harpy & Dundee. 
4to. pp. 63, pls. 4. Stockholm. 1903. 
