Briefe. 
123 
capriciousness as to the fertility or sterility of the crosses, as in other plants; but 
some points seem worth mentioning. 
The sterile unions between different species behave in most cases very 
differently from those of the self-impotent species. First withers the pedicel of 
the germen and the withering goes slowly on in an upwards direction, and even, 
when the germen falls off, pollen and stigma are generally fresh. Sometimes 
the pollen grows brownish; but then this discolouring generally begins at the 
outer surface of the pollen and but in very few cases at the inner surface where 
it touches the stigma, whilst the last is invariably the case in seif fertilized 
Oncidia. A germen of Cirrhaea fertilized with pollen of Stanhopea Jan. 24 was 
dropped only March 11. The pollen and its tubes which reached half way down 
the germen, were quite fresh. 
It seems that muCh more widely distinct species of Orchids may be success- 
fully crossed, than is usual with plants. I have unripe pods of Oncidium flexuosum, 
fertilized with pollen of Cyrtopodium, — of Notylia and Sigmatostalix fertilized with 
pollen of Ornithocephalus, — of the small Oncidium from Theresopolis fertilized 
with pollen of Sigmatostalix etc. But the most curious cases are the foUowing. 
Mr. Gautier a french coUector bad me, about six weeks ago, to cross for him in my 
garden Zygopetalum maxillare and Miltonia cereola. I did so, without expecting 
result. But all the crossed flowers of both the species have now fine swelUng pods. 
There seems to be no very close systematic affinity between the two genera; at 
least Miltonia is certainly much more closely allied with Oncidium (it is even united 
to this genus by Mr. Rchbch.). But, on crossing it with several species of Oncidium, 
I never obtained a seed-capsule. The only point, in which Miltonia cereola and 
Zygopetalum maxillare closely ressemble, is the colour of the labellum. 
March 6, when I crossed a Cattleya (probably a var. of C. elatior) with 
some other species of that genus and of Epidendrum I had just at hand some 
pollinia of Oncidium microp. and placed them on the stigma of a flower of the 
Cattleya; and this flower has produced a fine pod. — Probably the pollen-tubes of 
Oncidium will not be able to fertilize the ovules of Cattleya, and next month when 
the time of fertilization comes the pod will wither ; but even so the case is curious. 
The difference in result of reciprocal crosses of the same two species is 
often extremely great, and there seem to be certain species which have a great 
fertilizing power, but are fertilized with difficulty, while others are easily fertilized. 
The most interesting case, I hitherto observed, is that of Epidendrum cinna- 
barinum 
An Professor Hermann Müller, Lippstadt. 
Desterro, 30. Mai (Himmelfahrt) 1867. 
Lieber Bruder! 
Dein Brief vom 1 4. April kam vor wenigen Tagen hier an, und ich will den 
Rest des heutigen Tages benutzen, die Antwort wenigstens anzufangen. Ich 
komme eben ziemlich müde von einem Ausfluge nach der anderen Seite (nämlich 
der Meerenge) d. h. nach dem Festlande zurück, wohin ich gestern Nachmittag 
gegangen war, um mir ein 4 — 5 Stunden von hier wachsendes merkwürdiges 
Farrenkraut, Lygodium, zu holen. Du wirst es aus Darwin's Climbing plants als 
