HYBRIDISING AND RAISING ORCHID SEEDLINGS.  xxxv. 
incapable of being fertilised. An example will make this point clear. If 
the ovary of an ordinary flower—a lily for example—be examined as soon as 
the flower opens, the ovules will be found in a developed condition, so that 
when the pollen is applied to the stigma the pollen tubes grow rapidly, 
making their way down the tissue of the style, and into the ovary, when 
they enter the micropyle (or mouth) of the ovule, and unite with the contents 
of the egg-cell, this latter constituting the act of fertilisation, after which 
union the ovule develops into a perfect seed. But if an Orchid flower be 
examined at this stage the ovarian cavity and ovules will be found quite 
rudimentary, and if the flower is not pollinated they will progress no further, 
the flower at length shrivelling and falling off. But when pollinated a rapid 
change takes place. The column and ovary begin to swell and the segments 
to fade or change colour. The ovary often looks like a simple pedicel when 
the flower expands, but after pollination it gradually takes on a capsule-like 
appearance. The act of pollination applies a stimulus to the ovary, causing 
it to swell, and the ovules to develop, after which only can fertilisation take 
place. This retarded development of the ovary is one of the points in which 
Orchids differ so markedly from most other plants, and is, of course, 
correlated with the slow development of the pollen tubes. 
CaTTLEYA Moss1#.—In the case of Cattleya Mossiz the whole process 
has been worked out by Mr. Harry J. Veitch, who, by a series of experi- 
ments, ascertained the fact that fertilisation does not take place until a 
period of from 75 to go days after pollination. The process is briefly as 
follows: A few hours after pollination the floral segments become flaccid, 
and show signs of withering. Ina 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, and in eight days they have 
reached the base of the column, being found in vast numbers among the 
conducting tissues. At the end of a month the ovary has become consider- 
ably enlarged, and the placentze 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 enter the micropyle of 
the ovule, and fertilisation of the egg-cell is effected. It is noteworthy that 
before this event takes 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, entirely through the stimulus given by the act of 
pollination, and it enables one to realise to some extent why a seed pod may 
