442 BOTANICAL GAZETTE [DECEMBER 
their inorganic food, seeming quite dependent upon the presence of some 
form of potassium phosphate. This is particularly true of antheridia, and by 
varying the medium a filament may be obtained which bears no sex organs, 
or one bearing only oogonia, or one with oogonia and a few antheridia, or, 
finally, one with many antheridia some of which form fertilizing tubes. In 
this connection it should be recalled that specific distinctions have been based 
on the abundance of antheridia. In general the relation between oogonia 
and antheridia is such that support is given to the view of DeBary, viz., that 
the presence of oogonia induces the formation of antheridia. Dr. Klebs 
thinks this is due either to chemotaxis when proper inorganic salts are pres- 
ent, or that these salts render the twigs sensitive to the chemical stimulus 
emanating from the oogonia. It is evident, however, that normal oogonia 
can exist without inducing antheridial formation. 
While as conclusively proved in this research, there is no dominating 
inherent tendency toward an alternation of generations, nevertheless the con- 
ditions are such that in nature an alternation is usually brought about through 
the exhaustion of the nutriment afforded by each newly attacked host. 
Previous to oosphere formation the incipient oogonium may revert toa 
vegetative condition, but after the oospheres are differentiated the power to 
vegetate is irretrievably lost. This, the author thinks, is due to nuclear 
changes possibly to a chromosome reduction. 
An interesting chapter is given to the consideration of gemmee and the 
author concludes, apparently with ample ground, that they are of no signifi- 
cance in phylogeny. They are special structures whose function is to tide 
over times when the formation of other spores is precluded. They behave in 
general as do hyphae, and develop into oogonia or sporangia according to 
environment. Dr. Klebs closes by saying that an acquaintance with mere 
morphological marks does not constitute sufficient knowledge of a species. 
To meet his high ideal the systematist must hereafter determine, both quan- 
titatively and qualitatively, the life relations of the plant, its limits of varia- 
tion, and the stimuli that cause these variations.— F. L. STEVENS. 
WHETHER THE Saprolegniacez are exclusively apogamous or not is a 
question that has been argued fro and con in pre-cytological days by DeBary, 
Pringsheim, Cornu, Zopf, Ward, Humphrey, and others. Four years ago 
Messrs. Hartog and Trow almost simultaneously published papers expressing 
quite opposite views regarding fertilization in this group. Trow has recently 
made extended researches on Achlya® and arrives at conclusions in harmony 
with his earlier paper, He describes a karyokinetic division of the oogonial 
nuclei and a degeneration or digestion of the supernumerary ones, so that only 
* Trow, A. H.: Observations on the biology and cytology of a new variety of 
Achlya Americana. Ann. Bot. 193 1a1. 
