PBBBnART 27, 1914] 



SCIENCE 



313 



VII. SEXUALITY, CHROMOSOME HISTORY AND 

 ALTERNATION IN THE FUNGI, 1820- 



In this group of parasitic or saprophytic 

 thallophytes we shall find as great a variety 

 in the type of reproductive process as in 

 their mode of nutrition at the expense of 

 the hosts beset by them. At the beginning 

 of last century fungi were commonly sup- 

 posed to arise spontaneously "out of the 

 superfluous moisture of the earth and 

 rotten wood." 



Observations had been made long before 

 this, it is true, sufficient to render improb- 

 able the spontaneous generation of the 

 fungi then commonly believed in. Thus 

 Micheli (1729) had raised a fungus myce- 

 lium from spores. Ehrenberg (1820) did 

 the same and also saw the conjugation of 

 Sporodina. Du Trochet (1834) proved 

 that the mushroom arises from threads of 

 the mycelium in the soil. 



The spontaneous generation of even the 

 simplest of these parasitic or saprophytic 

 thallophytes — the bacteria — had been de- 

 nied by Leewenhoek at the end of the seven- 

 teenth century. In one his numerous 

 letters to the Royal Society he denies the 

 spontaneous origin of the animalculae or 

 bacteria which he found in the mouth. 

 These he found present even in the mouths 

 of ladies who clean their teeth carefully! 

 He insists that these organisms are like those 

 he had found in pools of water, and then 

 goes on to say, in a paragraph that reads 

 like a modern health commissioner's report: 

 Now when people wash their beer mugs and 

 drinking cups in the water from ponds and 

 streams, who can tell how many of these animal- 

 cute may stick to the sides of the glass and thus 

 get into the mouth. 



The hazy or bizarre beliefs concerning 

 the occurrence and the mode of repro- 

 duction in the fungi, current at the middle 

 of last century, were dispelled by the 

 studies of a group of able investigators 



early in the second half of the century. 

 First came the splendid work of the 

 brothers Tulasne (1847-1854) on the smute 

 and rusts, and their discovery of the oogon- 

 ium of Peronospora. Pringsheim in 1857 

 studied the sequence in development of the 

 zoosporangia and oogonia of the water 

 moulds. Then came the researches of that 

 master mycologist, Anton de Bary, on the 

 reproductive structures of Peronospora 

 (1861), of Pyronema and Sphcerotheca 

 (1863), and on the life histories of the 

 rusts, 1853 and 1865. The results of his 

 own work and that of his students Woronim 

 and Janczewski convinced de Bary that, ini 

 the Ascomycetes, as well as in the phyco- 

 mycetous Pcronosporas, the contents of an 

 oogonium is fertilized by the escape into it 

 of the living contents of the antheridiaj 

 tube that grows beside it. 



In the seventies and eighties a vast num- 

 ber of detailed observations concerning 

 reproductive processes in the fungi were 

 accumulated by many observers, led espe- 

 cially by 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 suc- 

 ceeded 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 oogonium of Saprolegnia^ 

 by the use of stained sections, and con- 



