re rT? 
1906] ATKINSON—AGARICUS CAMPESTRIS 261 
a variety, for it would seem that the four-spored quality or character 
is latent, since four nuclei are probably formed in the basidium in 
the normal manner but only two of them function. With regard to 
the cultivated forms of Agaricus campestris they probably represent 
also mutations either from Agaricus campestris or from some other 
species which has been confounded with it. Whether they are to 
be considered elementary species or varieties or retrograde varieties 
would depend upon their constancy or inconstancy, their stability 
or instability. They may be horticultural or domesticated varieties. 
Nevertheless it would seem that they have arisen by mutation. It 
is interesting to note in this connection that, whether species or 
varieties, if they have arisen by mutation their chances of becoming 
constant may be greater than in the case of plants which are well 
known to reproduce sexually. It is generally believed that the 
Agaricaceae are not reproduced by the cooperation of sexual organs. 
If,this is true, and if there is no process similar to fertilization, muta- 
tions of these plants would escape one of the operations in nature 
against the constancy of new mutants in species capable of cross 
fertilization, Some students regard the fusion of the two primary 
nuclei in the basidium as an act of fertilization, but from what we 
know of the origin of these two nuclei the possibility of cross fertili- 
zation of individuals at this epoch of development is excluded, though 
it cannot at present be regarded as impossible at an earlier stage in 
their ontogeny. Of course the earlier ideas of fertilization in the 
Agaricaceae held in the time of BULLIARD,3? who called the cystidia 
spermatic vessels and thought they squirted their juices on the seeds 
(Spores) thus bringing about fertilization, or by Corpa33 who regarded 
the cystidia as pollinaria and thought fertilization was brought about 
by the exudation of their fluid content to which the spores became 
attached and fertilized, are now unthinkable, as well as the notion 
of W. G. SurrH34 as late as 1875, who believed that filaments growing 
out from the cystidia came in contact with the spores and fertilized 
32 BULLIARD, Histoire des champignons de la France 1: 39-66. 1791. 
33 CorDA, Berich. Ises. 6:40. 1834; also Icones 3:44. 1839. See also H. Horr- 
eae eta und Spermatien bei Agaricus. Bot. Zeit. 14:137-148, 153-163- 
34 Situ, W. G., Reproduction in Coprinus radiatus. Grevillea 4:53-65. pls.. 
54-61. 1875. : 
