1904] CURRENT LITERATURE 235 
cyphus never occur on basalt or tuff, while Drepanium, Thuidium abtetinum, 
Brachythecium salebrosum, and Pottia latifolia are characteristic basalt plants. 
—G. H. JENSEN. 
IN A RATHER lengthy paper on embryonal substance, Nor13 discusses the 
various theories which have been announced regarding the controlling force in 
development, and presents some interesting observations on the protoplasm of 
the growing tip in Bryopsis, together with his interpretation of the latter. The 
facts, determined by very careful observation of the growing tips, are as follows: 
The protoplasmic circulation of the filament occurs throughout the whole plant, 
extending into the tip region as well as elsewhere; nevertheless the protoplasm 
of the apical portion is very different from that below. While the non-growing 
portions have only the usual thin protoplasmic layer lining the wall, that of the 
growing tip occupies the whole lumen. Also in the tip there are no chloroplasts, 
and the protoplasm is much more dense than elsewhere, while the nuclei are 
more numerous. Since the currents of cyclosis are constantly carrying new sub- 
stance into the tip and out again, there is a constant transformation of protoplasm 
at the limit of the denser region from somatic to meristematic and vice versa. 
At this limit the entering substance becomes more dense and the chloroplasts 
t 
Portions, it is impossible to suppose here that the meristematic protoplasm in 
the former region is fundamentally different from the somatic. The author 
concludes that, since the Hautschicht is the only part of the living substance 
which is constantly at the tip, and does not take part in the cyclosis, it must be 
in this that the controlling factor of growth is located. Thus he looks upon the 
Hautschicht of the tip as the only true embryonal substance here, and it does 
not contain nuclei. Therefore, he points out that in Bryopsis the factor producing 
Srowth does not lie in nuclei. The objection to this conclusion lies in the fact 
SPERMATOGE 
NESIS in Marchantia polymorpha has been reinvestigated by 
IkENno.4° In m 
any points this investigation has confirmed the earlier work of 
nd SCHOTTLANDER, but the more critical methods have made it 
D aS ; 
uring the early divisions in the young antheridium no nucleolus is demonstrated; 
saoithomncegadien| chromosomes is eight, as SCHOTTLANDER has already shown. 
oe eae ie Beobachtungen und Betrachtungen iiber embryonale Substanz. 
bs Sah 23: 281-297, 321-337, 401-427. 1903. 
Centralia se ey Die Spermatogenesis von Marchantia polymorpha. Beih. Bot. 
l. 15:65-88, pl. 3. 1903. 
