SEXUALITY IN PLANTS—JOHNSON. 401 
of the water molds. Then came the researches of that master 
mycologist, Anton De Bary, on the reproductive structures of Peron- 
ospora (1861), of Pyronema and Spherotheca (1863), and on the 
life histories of the rusts, 1853 and 1865. The results of his own work 
and that of his students Woronin and Janczewski convinced De 
Bary that, in the Ascomycetes, as well as in the phycomycetous 
Peronosporas, the contents of an odgonium is fertilized by the 
escape into it of the living contents of the antheridial tube that grows 
beside it. 
In the seventies and eighties a vast number of detailed observa- 
tions concerning reproductive processes in the fungi were accumu- 
lated by many observers, led especially be De Bary’s student, 
Brefeld. One outcome of this work which concerns our particular 
problem was the insistent, though unconvincing, denial by Brefeld 
of the sexuality of the Ascomycetes. 
In the last decade of the nineteenth century, with the application 
of new methods of fixing, sectioning, and staining, a new era opened 
in the study of sexuality in the fungi, an era in which American 
workers have played a prominent part from the beginning. 
As early as 1886 Rosenvinge had succeeded in staining the many 
nuclei of the mycelial cells of toadstools; also the primary basidium 
nucleus and the four-spore nuclei arising from this. 
Humphrey (1892) and Hartog (1895) followed the history of the 
nuclei in the antheridium and oégonium of Saprolegnia by the use 
of stained sections, and concluded, as De Bary had done, that there 
is no fertilization in these forms. Not until the work of Trow (1904) 
and Claussen (1908) was it proven that the antheridium of these 
water molds, at least in some species, may be functional, and not 
always vestigial, as De Bary (1881) and Humphrey had thought. 
The earliest cytological work on the Ascomycetes, after the detec- 
tion of their nuclei by Schmitz, was that of Dangeard (1894), He 
described and figured a fusion, of two nuclei in the ascus of Exoascus, 
of Peziza, of the truffle, and others. The source of the two fusing 
nuclei Dangeard did not trace back farther than the subterminal cell 
of a hooked hypha, from which the ascus arises in Peziza and others. 
The ascus, with its fusion nucleus, he regarded as an odéspore. 
In 1895 there was announced from Strasburger’s famous laboratory 
at Bonn a discovery which seemed at one stroke to settle the dispute 
between De Bary and Brefeld, and to definitely demonstrate the 
occurrences of a sexual nuclear fusion in the sexual organs seen by 
De Bary. In that year Harper showed that out of the opened 
antheridial tube of the hop mildew, Spherotheca, a male nucleus 
passes into the odgonium and fuses with its nucleus. The whole 
behavior of antheridium and oégonium and their contents had 
73176°—sM 191426 
