316 BOTANICAL GAZETTE [APRIL 
It APPEARS from Poropko’s work on the growth of bacteria and molds under 
different pressures of oxygen,3? that the maximum pressure of this gas which can 
be borne varies, in twenty-five organisms studied, from 0.676 to g.38 atmospheres. 
A single nutrient medium was used throughout, and the author points out that 
with other media perhaps the maximal pressures might have been different. 
The upper limit of oxygen pressure for optimal growth seems not to be related 
to the maximal pressure. Furthermore, every aerobe has its specific minimal 
pressure of the gas. This point lies considerably higher for the molds than for 
bacteria, being about 0.6 atmospheres for Aspergillus, Penicillium, and Mucor, 
while it is 0.00016 for Bacillus subtilis. Of course, in case of facultative anaerobes 
there isno minimum. The lower limit for most obligate aerobes lies low enough 
to allow the growth of obligate anaerobes.—B. E. LivincsTon. 
Miss ROBERTSON,33 in continuing her study of Torreya californica, has 
described the sexual structures and fertilization. Two to four archegonia are 
produced, the neck consisting of a single tier of four or six cells. The division of 
the central cell was observed, and an ephemeral ventral nucleus inferred. The 
two male nuclei were observed in a common cytoplasmic sheath, but no inequality 
in the male cells was noted. In fertilization the cytoplasm of the male cell was 
observed investing the fusion nucleus. In the development of the proembryo 
wall-formation occurs after four free nuclei have appeared. A count of chromo- 
somes indicated that the reduction number is eight. The general conclusion is 
reached that the morphological evidence does not bear out the suggestion of se 
dean resemblances obtained from the anatomy of the seed and seedling. —J.M. 
Grécorre+ has investigated the reduction of chromosomes in the pollen 
mother-cells of Lilium speciosum and Allium fistulosum. The immediate occa- 
sion for the investigation was that STRASBURGER’S recent conclusions** conflict 
with those of BERGHS,3° a pupil of Grécorre. The present investigation con- 
vinces Grécorre that his pupil is correct in his interpretations, and that STRAS- 
BURGER’S recent interpretation of mitosis in Thalictrum purpurascens will not 
apply to Lilium, Allium, and Convallaria. The most interesting mgm 
in the present paper concerns alternations of generation. GREGO RE claims 
that since reduction is not complete until the four spores are cam anion the 
32 PoropKo, THEODOR, Studien iiber den Einfluss der Sauerstofispannuns auf 
pflanzliche Mikroorganismen. Jahrb. Wiss. Bot. 41:1-64. 1904 
33 ROBERTSON, AGNES, Studies in the morphology of Torreya cali wii 
sexual organs and fertilization. New Phytol. 3:205-216. pls. 7-9. 1904 
ia, 1. ‘The 
34 GREGOIRE, Victor, La réduction numérique des chromosomes et les cine 
de maturation. La Cellule 21: 297-314. 1904. 
: - XK, Preus. 
35 STRASBURGER, Epuarp, Ueber Reduktionsteilung. Sitzungsb. K. K. Pr 
Akad. Wiss. 18:—: [1-28.] 1904. See Bor. GazeTre 38:397-398- 1994: 
TO- 
3° BERGHS, JULES, La formation des chromosomes hétérotypiques oe a tak 
géntse végétale I. La Cellule 21:173-189. 1904. See Bor. GAZETTE es 
