Briefe. 
useless to, but even act as a poison to each other! Thus, four or five days after 
fertilization a brownish colour appears on the adjoining surface of the pollen and 
Stigma and soon afterwards the whole polHnium is rendered dark-brown. 
This is not the case when you bring instead of own pollen, the pollen of 
widely different species on the stigma of Oncidium flexuosum. Among others I 
tried the pollinia of Epidendrum Zebra (Fig. 32) (nearly allied to, or perhaps 
not specifically distinct from Ep. 
variegatum). Of course no seed- 
capsules were produced; 8— g days 
(in one out of about 20 flowers 
12 days) after fertilization the 
germs began to shrink, but even 
then the pollen and its tubes which 
sometimes had penetrated in the 
Upper part of the germ, had a 
perfectly fresh appearance, rarely 
showing a very faint scarcely per- 
ceptible brownish colour. — The 
pollinia of Ep. fragrans also I 
found to be perfectly fresh, as well 
as their tubes after 5 days stay in 
the stigrnatic Chamber of On- 
cidium flexuosum. 
The poisonous action of own 
pollen becomes still more evident, 
on placing on the same stigma 
two different pollen-masses. In a 
flower of Oncidium flexuosum, on 
the Stigma of which I had placed 
one own pollen-mass and one of 
a distinct plant of the species, I 
found five days after the former 
brown, the latter fresh; in some 
other flow^ers 4 or 5 days after 
both the pollen-masses M^ere brown, 
and I think, although my experi- 
ments are not yet quite decisive, 
that own pollen will always kill 
the pollen of another plant when 
placed on the same stigma. — 
Now compare this destructive action 
of own pollen with that of Epi- 
dendrum (species allied to varie- 
gatum). 
Debr. 15 I placed on the Stigmas of some flowers of One. flexuosum one 
pollen-mass from a distinct plant of that species and one of Epidendrum. — 
Debr. 21^ both the pollen-masses fresh melting with numerous tubes. — Dec. 26 
Fig. 32. Epidendrum Zebra. Aus dem Nachlass. 
