160 THE JOURNAL OF BOTANY 
forms’”’ of FE. Graminis on Bromus interruptus, B. herdeaceus, B. com 
mutatus, B. tectorum, and B. arvensis, T’ riticum, and Avena, and of 
fu 
pee es obtained was considered by Marchal to prove the pbanien 
ng 
bcialisées.”’ 
aes abe serene tore maritimum, pid al et bulbosum.” 
This ‘* forme epéoialisée * a ‘Hoi proved to be unable to infect yas 
wheat, or oats, or indeed a other species of grass on which i 
was sown in an experiment in which forty-eight species of eae 
belonging to twenty-seven different genera were use 
Now in all these experiments the conidial stage only of the 
fungus has been used, and in considering the question of the dis- 
tinctness of * biologic forms” in the Erysiphacee, one has been 
compelled, from the absence of any information on the subject, to 
cue out of consideration the infection-powers of the ascospores. 
It is obvious that the whole problem concerning the distinct- 
ascospores of e ach form. er has poe ‘the opinion that it 
is probable that the ascospore erve as a connecting link between 
** biologic forms.’’ Neger supposes er in the case of two ‘‘ biologic 
as t-plan 
the other. Neger cites as evidence in support of this view certain 
phenomena he has observed in the case of some species of ci 
on certain host-plants. He observes (t, p. 270): “Der Umstand 
aber, dass auf einjabrigen | Pflanzen, . B. ary eugaris i 
welchem also M st), eine Hrysiphe 
sich in eee Jahr reichlich entwickelt, ohne cndieas sen ie zur Peri- 
thecienbildung zu gelangen, legt die Vermuthung nahe, dass mittelst 
der Ascosporen die Uebe ertragung eines Mehlthaupilzes von einer 
Art auf eine andere (Wirthpflanze) wohl méglich ist. Demnach 
waren die Ascosporen dadurch ausyezeichnet, dass sie das Bestreben zeigen, 
den Kreis der Wirthpflanzen eines Pilzes weit zu erhalten, wahre end die 
Conidien eo sehr schnell einem bestimmten Substrat anpassen.’ With 
regard to the phenomena quoted I have elsewhere given reasons for 
considering wei the deductions drawn by Neger are hardly ai 
anted. On priori grounds, however, it certainly seemed likel 
that the siccniaves might prove to be able to infect host-plants of 
the species which the conidia of « biologic forms ’’ were unable 
pee feo ge however, it may be noted, inclines to the opposite 
This author remarks (5, p. 212), : eomnechien with the 
“ biologie forms sp of R, Graminis studied b ‘* Comment se 
sijaldlbpiquss étudiées? 
Contribuent-elles i fixer d'une fagon plus profonde, définitive, dans 
la descendance, l’étroite adaptation parasitaire acquise ? bien 
