THE ORCHID REVIEW. 167 
and hardy species of Cypripedium, but hitherto without success, and it 
seems highly probable that the very diverse conditions under which they 
grow, coupled with their constitutional differences, form an insuperable 
barrier to their union. Numerous efforts have also been made to cross 
the tropical Cypripediums with the American Selenipediums, and not 
wholly without success, for a few seedlings have been raised, but. the 
number of failures is sufficient to prove that they do not unite very readily. 
Attempts to intermix Masdevallia Chimera. and its allies with the brilliant- 
flowered species have generally ended in failure, though we believe such 
a seedling has now been raised. Calanthe vestita, it is said, refuses to 
cross with the species of the C. veratrifolia group, yet, singularly enough, 
it hybridises readily with Phaius grandifolius. 
Sometimes a cross is effected and a capsule produced which is to all 
appearances perfect, but on dehiscing the placente show nothing but the 
remains of the shrivelled ovules, and in these cases it is doubtful whether 
fertilisation proper has ever taken place. In this family, as is now pretty 
well known, a considerable period elapses between the pollination of the 
flower and the fertilisation of the ovules—in the case of Cattleya Mossi 
as much as from seventy-five to about-ninety days, as proved by experiments 
made in Messrs. Veitch’s establishment. When the flowers expand the 
ovary and ovules are in a very rudimentary state, but the act of pollination, 
or the application of the pollen to the stigma, applies a stimulus to the 
ovary and causes it to swell. The effect is visible after the lapse of a few 
hours, as the floral segments become flaccid and show signs of withering. 
In a couple of days the pollinia are seen to be disintegrating, forming, with 
the viscid secretion from the stigma, a gelatinous mass that quite fills up 
the stigmatic cavity. At the same time the pollen tubes have commenced 
to grow. Ineight days the tubes have reached the base of the column, 
being found in vast numbers among the cells of the conducting tissue. At 
the end of a month the ovary has become considerably enlarged, and the 
placente and ovules are beginning to assume a definite form, while the 
pollen tubes are pushing downwards along the sides of the placente and 
among the ovules. In two months, though the pollen tubes are present in 
countless numbers, and have even reached the base of the ovary, the 
ovules are not yet developed, but soon afterwards they rapidly undergo 
a change of form, and at the end of about three months the long-looked-. 
for event takes place. The pollen tubes now come into contact with the 
apex of the ovule, and fertilisation is effected; after which alone the 
embryo is developed. 
It is noteworthy that before this event alien place the ovary has 
developed from a terete body, less than a quarter of an inch in diameter, 
to a six-angled one, more than seven times as broad, and as a mere result 
of the stimulus given by the act of pollination and the subsequent growth 
