482 BOTANICAL GAZETTE [JUNE 
parasitic; while facultative parasites are attracted by substances, such as 
sugar, common to many plants. That a facultative parasite does not attack 
all plants containing sugar is probably due to the presence of some other 
negatively chemotactic substance in the plant. A state of immunity, there- 
This was actually eed to be the case with an immune cucumber plant 
growing among a number of plants attacked by Dendryphium comosum. All 
efforts to inoculate plant failed. The germ tubes of the fungus also 
failed to respond chemotactically to a decoction of the leaves of the plant. 
Miyoshi has shown that by pee leaves with a sugar solution the germ tubes 
of Penicillium oa z could be e to penetrate the leaf and grow in its 
tissues. By a similar method nas has succeeded in growing 77richothe- 
ctum aa on begonia leaves injected with 2 per cent. sugar solution. 
The spores produced in the first instance were sown on another injected leaf 
and so on for fifteen SS Sowings from some of the later gener- 
ations of spores were made on leaves not injected, and it was found that the 
fungus grew and pniele on the leaf; in other words, it had been changed into 
a true parasite in twelve to fifteen generations. In several other instances 
similar experiments were successfully carried out with other fungi and other 
hosts, and several itlus trations are given where a similar transition was 
observed. in nature. The transition from a saprophytic to a parasitic mode of 
life is thus shown to take place with comparative ease, The possibility of 
ie 
appear evident, not only in its relation to parasitism among fungi, but also as 
an explanation of the curious phenomena of heteroecism and symbiosis.— H. 
HASSELBRING, 
STRASBURGER® has made a careful investigation of the origin of the 
embryo sac and development of the prothallium in 7arus baccata, The 
work was undertaken not with the expectation of making new discoveries, 
but rather in the hope of Ren a firmer basis for comparison with the 
problematical structures of the embryo sac of angiosperms. Each embryo 
c mother-cell in Taxus is the inner cell of a row resulting from repeated 
divisions of an outer ate of the periblem of the nucellus. The sporogenous 
cells in the nucellus form a group of from three to five coateses embryo 
sac mother-cells only slightly marked off from the surrounding tissue, which 
in a physiological sense may be designated as a tapetum. The mother- ae 
are formed in October and the winter is passed in this condition, but b 
end of February they have elongated so that they are readily ee 
The spring of 1903, when the material was collected, was unusually early, so 
that the pollen was shed by the last of February, and about the same time 
3* STRASBURGER, EDUARD, Anlage des Embryosackes und Prothalliumbildung 
bei der Eibe nebst anschliessenden Erérterungen. Reprint from Festschrift zum 
siebzisten Geburtstage von Ernst Haeckel. pp. 1-18. p/s. 7-2. Jena, Gustav Fischer. 
1904. 
