382 DIVISION III,—MODE OF LIFE OF THE FUNGI. 
its cultivation, though they may supply unequal amounts of nutrient material. On the 
other hand it by no means attacks every kind of Phanerogam as a parasite. I was 
unable to find, after repeated and careful search, any trace of the Fungus on the plants 
of a moist meadow close to the beans above mentioned. Among plants under cultiva- 
tion one variety of Phaseolus vulgaris in the same garden was very slightly infected 
with the Fungus in spite of the immediate proximity of the others. Experiments 
in inoculation also showed that Phaseolus multiflorus was scarcely ever attacked ; in 
other specimens the Fungus developed only scantily, but in single young seedlings kept 
very moist its growth was vigorous. Living plants of Brassica (B. rapa, B. Napus, 
and B. oleracea) were never attacked, either as young seedlings or as plants ready to 
blossom. Further details must be reserved for another place. 
It should be added, that the hyphae of the Fungus when once they have become 
capable of infecting make their way into the superficial living cells by piercing their 
walls, and grow indiscriminately in and between and through the cells of the living 
tissue and soon kill them. The power of infecting is shown by the power of penetrating 
the membranes, which are evidently dissolved at the points of penetration. Hence it 
is very probable that this power depends on the presence of a substance which can 
dissolve a membrane, a ferment in fact, and that this substance is not formed and 
discharged in sufficient quantity till the germ-tube from the spore is properly nourished 
and developed. 
The foregoing statements with regard to the power possessed by Sclerotinia Sclerotiorum 
of infecting are in opposition to some which have been published in other works and 
especially in Frank’s Pflanzenpathologie, p. 530 ff. ; according to these accounts the young 
germ-tube has the infecting power without previous preparation, and plants of Brassica 
were at once attacked by the Fungus. The observations may be correct in both cases 
and the difference may arise from the fact, that several species resembling one another 
in ‘appearance, but differing in the mode of vegetation, are confounded together under 
the name of Sclerotinia Sclerotiorum. The discussion of this point would occupy us 
too long and must be reserved for another occasion. 
Among other species of Pythium' which have been carefully examined Hesse’s P. 
de Baryanum is a parasite on living and healthy plants, and attacks them both with 
its germ-tubes which are formed in water and with the branches of the mycelium, 
when it has acquired strength. It attains its full development equally well on dead 
vegetable substances and on the dead bodies of animals, and is therefore equally a- 
saprophyte and a parasite. In the latter character it penetrates into the cells of a 
great variety of Dicotyledons and Monocotyledons and into the prothallia of Ferns, 
but leaves plants of Spirogyra and Vaucheria untouched. Some Phanerogams are 
also said to be secure from its assaults, but this statement requires confirmation. It 
attacks with especial readiness and frequency the young and watery seedlings of 
Phanerogams such as the Cruciferae and Amarantus, taking possession of them and 
destroying them rapidly and completely. Full-grown land-plants are usually less readily 
attacked and the injury done to them is more local; but they too may be rapidly 
destroyed by the Fungus if they are placed in water. 
Other and nearly allied species of Pythium are, as far as is known, partly pure- 
saprophytes, partly facultative parasites within narrow limits, P. intermedium and 
P. megalacanthum grow as saprophytes on dead parts of plants. They leave living 
Phanerogams, even young seedlings which are so liable to the attacks of P. de Bary- 
anum, always and absolutely untouched ; but P. intermedium readily attacks the 

1 Bot. Ztg. 1881, p. 531. 
