AND THEIR MORPHOLOGY. 183 
on the relative space which the organ occupies on the axis at the 
time of its origin, and that their subsequent multiplieation is 
equally dependent on the quantity of tissue which composes the 
organ in question. 
If we look upon the labellum as a simple organ, the family is 
variously connected with the remainder of the Monocotyledons, 
and the labellum finds its analogue in various families of both 
great divisions of the vegetable kingdom (Phanerogams). At the 
same time the column must contain the nine interior organs of 
the flower, or, as I would express it, it is here where they partly 
have not made their appearance. 
R. Brown, as is well known, first showed the great import- 
ance of organogenetie studies in questions of this kind. He was 
not led by them in this ease, not perhaps admitting that these 
investigations are always decisive. Others, myself amongst the 
number, have tried to solve the question in this manner, and 
finished by owning that the decision was doubtful Yet, if we 
consider how many other dark points have been settled by such 
research, I think the soberest course will always be to try our 
morphologie speculations on the touchstone of the same, and to 
accept nothing that has not been ratified by it. 
It will be sufficient to describe shortly the development of the 
Orchid flower to bring out the important points which bear on 
the question at issue. I shall choose a common plant, Catasetum 
tridentatum. The three sepals appear at the same time, and are 
followed immediately by the two lateral petals. The labellum 
makes its appearance only after these, which accounts for its being 
generally partly covered by them. As the axis grows during this 
time, the labellum stands a little higher on it than the petals 
which theoretically belong to the same whorl. Nearly simul- 
taneous with the appearance of the labellum is that of the anther, 
but the former occupies a larger space on the part of the flower 
where both are situated. 
After this the flower becomes more hollow at the bottom, and 
the first traces of the ovarian cavity appear. The next organ 
which becomes visible is the anterior segment of the stigma, as a 
searcely perceptible swelling between the upper end of the 
anther and the ovarian cavity (figs. 7 & 8,7). The next ehange we 
observe is the appearance of two smaller swellings under the 
labellum (fig. 11), which, however, soon merge into one (fig. 13), 
while the anterior lobe takes a rapid development (figs. 9, 10, 12). 
While in this instance the two posterior lobes of the stigma, 
