Fepruary, 1912.! THE ORCHID REVIEW. 37 
countless numbers. Meantime the ovary steadily thickens, and _ the 
placentz and ovules gradually develop, until they reach the mature stage 
seen in many ordinary flowers at the moment of expansion. Then only is 
fertilisation effected. 
Dr. Hildebrandt found that the period elapsing between pollination and 
fertilisation in Phaius grandifolius was about two months, and_ in 
Dendrobium nobile and Cypripedium insigne four months, while in Orchis 
and other European terrestrial Orchids the process was complete in eight 
to fourteen days. In the case of Cattleya Mossiw, Mr. Veitch found the 
period to be about three months. Prior to fertilisation the pollen tubes 
have penetrated the ovary in countless numbers, and lay along the 
placentz and among the ovules, which are rapidly undergoing the change 
of form that indicate maturity. This stage being reached, the pollen tubes 
enter the micropyle of the ovule and impregnation takes place, the effect of 
which is to cause the ovules to develop into seeds. 
It is a remarkable fact that the pollen of quite distinct genera of Orchids 
will cause the development of the ovules without subsequently effecting 
fertilisation, and this is believed to be the reason why the capsules of some 
crosses decay or open prematurely and contain nothing but “ chaff.” It has 
been shown that the young capsule is at least partly formed before 
fertilisation is effected, and should the latter not take place—from whatever 
~cause—the ovules fail to develop into seeds. 
This brings us to the numerous “false” hybrids of Zygopetalum, and 
the question arises whether in these cases fertilisation takes place or not. 
Pollination from the most diverse genera of Orchids serves to cause the 
development of the ovary and ovules, and the latter further develop into 
seeds, which, however, only reproduce the mother plant, and thus are not true 
hybrids. It is not known how far the diverse pollen tubes develop, nor yet 
whether they enter the micropyle of the ovule and effect fertilisation, The 
latter case would indicate complete maternal dominance. On the contrary, 
should fertilisation not take place the inference would be that the stimulus 
of pollination had not ceased with maturation of the ovules, but that they 
had developed further into parthenogenetic buds, capable of reproducing the 
species. With other species of Zygopetalum true intermediate hybrids are 
produced, also with Colax, showing that fertilisation takes place. The same 
must probably be said in the case of Chondrorhyncha, for Chondropetalum 
Fletcheri is not identical with the Zygopetalum, though closely resembling 
it. It is said that the result is the same when the Chondrorhyncha is 
the seed parent, and if this is really the case the evidence is conclusive. 
Clear evidence of such a case of paternal dominance would be remarkable, 
and we should like to see the cross repeated. In no other case, so far as we 
can learn, has the reverse cross been successful, but evidence is wanting as 
