No. 5.— OBSERVATIONS ON THE CYTOLOGY OF 
ARAIOSPORA PULCIIRA THAXTER. 
BY CYRUS AMBROSE KING. 
Introduction. 
The simultaneous publication, in 1895, of the investigations of 
Hartog and Trow, in which such diverse conclusions were reached 
in regard to the existence of sexuality and the manner of producing 
uninucleate oospheres in the Saprolegniaceae , and the interesting 
results obtained the next year by Wager in his classic paper on 
Cystopus Candidas, have suggested and stimulated an investigation 
of the cytology of various Oomycetic Phycomycetes. The appear¬ 
ance in the meantime, of papers by Berlese (’97), Trow (’99), 
Stevens ( 99), Lagerheim (:00), Davis (:00), Wager ('.00), Stevens 
(:01a), Trow (:01), Stevens (:01b), and Miyake (:01), all on the 
cytology of this subgroup, indicates a gradually increasing interest 
in this field of research. 
In the spring of 1898, the writer, at the suggestion of Prof. 
Roland Thaxter, of Harvard university, with whom he was then a 
student, began collecting material for a cytological study of 
Araiospora pulchra Thaxter, one of the Leptomitaceae , which is 
fairly abundant in the vicinity of Cambridge. As all the members 
of the order are aquatic and several have a generally similar habi¬ 
tat, the writer, in the progress of this work, which was carried on 
with some degree of regularity for two seasons, gradually accumu¬ 
lated and fixed material of a number of related genera. 
Thaxter (’96) in an examination of living material of Araiospora 
pulchra , saw and figured stages in the development of the oogonia 
and antheridia as well as the antheridial proto plasm in the process of 
entering the oosphere. The primary purpose of this investigation 
was, therefore, to learn the details in regard to the development of 
the sexual organs and of fertilization. 
As has been suggested, the work was begun in the Cryptogamic 
laboratoiy of Harvard university where a portion of it was finished 
and where all the material was? fixed and prepared for cytological 
