230 BOTANICAL GAZETTE [MARCH 
FIscHER has also investigated the biology of Armillaria mucida,? more 
especially with a view to determining whether the fungus is a parasite or a sapro- 
-phyte. Most writers simply state that the fungus grows on beech trees, but 
MassEE records that “‘at High Beech, Epping Forest, . . . . a healthy branch 
of a beech having been broken off, the wound was inoculated with the spores of 
A. mucida. At the end of the second season after the inoculation the branch was 
killed for a considerable distance, and the sporophores of the fungus appeared 
in abundance.”” FIscHER, unwilling to accept this observation as proof that the 
fungus is a parasite, has attempted to infect wounds made in living beech trees. 
with spores or with mycelium. His experiments gave negative results, so that 
he was unable to obtain any proof of the alleged parasitism of the fungus. On 
the other hand, he found that the fungus could be grown readily as a saprophyte 
on various substrata, such as bread, dead beech wood and twigs, and also upon 
gelatin containing beerwort, meat extract, or malt extract. The time elapsing 
between the sowing of the spores and the ripening of the fruit bodies in pure 
cultures varied from 51 to 109 days. The spores germinate readily in water as 
well as in various culture media. FiscHer’s inoculations were carried out on 
thin branches. Possibly, if stouter branches containing older wood had been 
used, positive results might have been obtained. So far, however, there does not 
seem to be any clear evidence that the mycelium of A, mucida can kill the living 
parenchyma and medullary ray cells in beech wood. 
FIscHER states that a spore, after arising somewhat laterally on its sterigma, 
“only assumes the central position later on as it approaches maturity.” The 
figure given of the mature basidium does not support the statement that the spore 
is situated symmetrically over the sterigma. If FIscHER’s observation is correct, 
then Armillaria mucida is a marked exception to the general rule for the position 
of the mature spores in Hymenomycetes. There is one misquotation, doubtless. 
due to a printer’s error, from a paper by the writer. The number of spores that I 
found to have been produced from a large fruit body of Polyporus squamosus 
was II,II2,500,000, and not 11,112,500 as stated.t° FiscHER urges that since 
the number of spores produced from a fruit body is so vast, wounds on trees must 
often become infected, and that stumps or timber infected with Armillaria mucida, 
as well as its fruit bodies, should be destroyed when possible. It may be added 
that eleven thousand million spores would be sufficient to provide one for each 
q inch i ly tl 1 iles of level ground.—A. H. REGINALD BULLER- 
Chemotropism of pollen tubes.—In 1889 Moxiscu showed that pollen tubes. 
grow toward pieces of the stigma (chemotropism), and grow away from the edge 
of a cover-glass preparation (aerotropism). Five years later MrvosHt found that 
9 FiscHer, C. C. E., The biology of Armillaria mucida Schrader. Annals of 
Botany 23:515-535. pls. 36, 37. 1909. 
10 BULLER, A. H. R., The biology of Polyporus sgquamosus Huds., a timber-destroy- 
ing fungus. Jour. Econ. Biol. 1:114. fig. 6. 1906; also Researches on Fungi. Part y 
chap. 5, 1909. London: Longmans, Green & Co. 
