540 BOTANICAL GAZETTE |JUNE 
alpine flora is extremely diverse in floristic composition; (3) the rare species 
are most numerous and the common species least numerous (this does not apply 
to number of individuals); and (4) the C.c. is generally higher for contiguous 
than for distant areas. This last result is strikingly demonstrated in the 
study of the vegetation upon some alpine gravel areas™ of the Alps. In this 
latest report JACCARD also makes extensive use of his generic coefficient (coeffi- 
cient générique; C.g.), that is, 
No. of genera X 100 
=C.g. 
No. of species : 
with instructive results. This coefficient is shown by studies of both alpine and 
dune floras to vary inversely with the variety of ecological conditions in the 
areas compared, and hence in alpine areas the value of C.g. increases with 
altitude, while in some dune areas of Belgium, the C.g. is greatest (100) under 
the excessive and narrow ecological limits of the moving dunes, and least (73) 
under the more varied ecological conditions of the pannes. 
hese analyses lead the author to the following among other conclusions: 
(1) The distribution of plants (at least in the alpine zone) is a resultant of the 
combined action of three orders of factors; (a) ecological, (b) biological, or 
degree of adaptation, and (c) sociological, or competition between species; and 
(2) the action of these factors has resulted in (a) an eliminative selection of 
species, and (0) a distributive selection determining the number of individuals 
and the nature of associated species.—Gro. D. FULLER. 
Tetraspore formation in Nitophyllum.—Since it has been shown that in 
Polysiphonia and Dictyota the reduction of chromosomes occurs during the 
formation of tetraspores from the tetraspore mother cell, it is natural to inquire 
what cytological conditions obtain during tetraspore formation in those red 
algae which have multinucleate cells. One might guess that the tetraspore 
mother cell is uninucleate, or that it is multinucleate and all the nuclei except 
one disorganize. Soon after YAMANOUCHI’s paper on Polysiphonia appeared, 
SVEDELIUs examined Martensia, one of the Delesseriaceae. The tetraspore 
mother cell is paige and, as the cell enlarges, the nuclei multiply until 
there are about fifty. n all but one disorganize, and four tetraspores are 
formed. The fixing did n not allow a detailed cytological study. Recently, 
however, SVEDELIUS” secured well fixed material of Nitophyllum punctatum, 
a member of the same family, and succeeded in working out the cytological 
situation. The thallus is prevailingly one cell thick, but when tetraspores 
are so formed, it becomes three or four cells thick. The tetraspore mother 
™ JAaccarD, P., Etude comparative de la distribution florale dans quelques forma- 
tions terrestres et aquatiques. Rev. Gén. Botanique 26:5—21, 49-78. 1914. 
2 SveDELIUs, N., Uber die Tetradenteilung in den vielkernigen Tetrasporangium- 
anlagen bei V sas sleet punctatum. Ber. Deutsch. Bot. Gesells. 32:48-57. pl. 1. 
1914. 
