1906] CURRENT LITERATURE 79 
shallows, in contrast to the above, plants are the more efficient land-builders; 
the developmental processes in such places are well known and need not be 
recounted here. ARMING also speaks of sandy plains that are subject to occa- 
sional inundation. Here algae play a great part in soil-making; it is common 
for a layer of Phycochromaceae to penetrate for three to five centimeters into the 
sand, cementing the grains together, and giving a greenish appearance to the 
ground. Many of the diatoms characteristic of such places are listed by habitats. 
The peculiar depressions of salt marshes, called ‘‘pans”’ by OLIVER and TANSLEY, 
are thought by WARMING to be formed where heaps of decaying vegetation have 
lain; the consequent destruction of the vegetation makes it easy for the waters to 
wash out the soil in such places.—H. C. Cow es. 
Periodicity of sexual organs in Dictyota.—WILtAqs, in the third contribution 
to his series of Studies in the Dictyotaceae,'3 discusses the remarkable periodicity 
in the formation of the sexual cells in Dictyota. The sexual organs are produced 
during the fruiting season in fortnightly crops, synchronous with the spring Sa 
and a general liberation of the gametes takes place on a particular day, at a 
interval after the highest spring tide, varying, however, in different localities 
Of the factors (temperature, pressure, aeration, etc.) which fluctuate with the 
alternation of neap and spring tides, the one which seems to account most satis- 
factorily for the facts of periodicity is the increased illumination of the plant 
during the low water of spring tides. The times of initiation and liberation may 
be slightly accelerated or retarded by exceptional meteorological conditions, as 
when wind causes a difference of two or three feet in the height of water, or a 
rise of one inch in the barometer accompanies a depression of six or seven inches 
in the tide—B. M. Davis. 
Brown pigment of algae.—The generally SE view that the color of the 
chromatophores of the brown algae and diatoms res the presence of 
a brown pigment, phycophaein, in addition to " Madipbyll is challenged by 
Mottscn,'+ who believes that the phycophaein garcons from these algae is a 
post mortem product. He holds that the brown pigment is a + tie substance, 
phaeophyll, which passes readily over to chlorophyll ates poabole with hot water, 
alcohol, and other fluids. A similar brown pigment is found in the orchid, 
Neottia nidus-avis. Beside the phaeophyll, 20 brown pan “ag diatoms contain 
carotin and a bluish-green pigment, leucocyan 
racts of Bennettites —LicNier's from a reexamination a his preparations 
of che involucral bracts of Bennettites Morierei concludes that in all the sterile 
scales, superficial or otherwise, which enter into the composition of the strobilus, 
the terminal enlargement is due to hypertrophy and does not result from a reduc- 
tion of the bract.—W. J. G. Lanp. 
*3 Witiiams, K. L., Studies in the — tik; The origami of the 
sexual cells in Dict yota dichotic’. Ann. Botany 19:531-560. figs. 6. 1905. 
™4 Motiscn, H., Ueber der braunen behead der Phaeophyceen und Diatomeen. 
Bot. Zeit. San. sone pl. O- 1905: 
1SLIGNIER, O., Notes  aaamacet ines sur la structure du Bennettites Morierei. 
Bull. Soc. Linn. Norwaidie V. 8:(pp. 7.) 1904- 
