100 
JOUEXAL OF THE ROYAL 
HORTICULTURAL 
SOCIETY. 
OBSERVATIONS ON SOME OF THE PLANTS EXHIBITED. 
By the Rev. Prof. G. Henslow, M.A., Y.M.H. 
[Delivered June 27, 1899.] 
Orchids. — After calling attention to the remarkable similarity in the 
flowers of some Orchids to insects, as in that of the Bee," the Fly," 
the "Butterfly," and Oncidium impilio, the lecturer described the 
curious processes of polhnation by insects in Orchis viaculata and 
Catasetum, as explained by Darwin in his work on The Fertilisation of 
Orchids." He observed that, with all their elaborate structures adapted 
for intercrossing, Orchids were, as a rule, so far as the production of seed 
was concerned, much worse off than other flowers which could fertilise 
themselves ; since in most kinds the pollen masses could not be removed 
w^ithout insect agency, and if the proper visitors failed to come they bore 
no seed at all. On the other hand, those species which can effect their 
own pollination, as the "Bee " Oplirys apifera, Ckjjsis aiirea, and some 
cleistogamous species of PJiaius, Arundinia, Eria, &c., set an abundance 
of seed. Darwin's dictum, " Nature abhors self-fertilisation," had been 
proved to be as groundless as " Nature abhors a vacuum." ^Yere the 
latter true, she would have long ago put some stop to our having incan- 
descent electric lights ! 
Eryngium. — A species of this genus illustrated one of the numerous 
instances of plant mimicry, in that having its flowers grouped in a 
massive head, with an involucre of bracts, it greatly resembled a Thistle 
in outward appearance, but the structure of the flowers and fruit revealed 
the fact of its not being a composite, but an umbelliferous genus. 
Iris, Gladiolus, Crocus, and Ixia. — These four genera, so unlike 
€ach other, all belong to the family Iride^, inasmuch as they agree in 
having only three stamens instead of six, the usual number in 
Monocotyledons, while the anthers burst outwards instead of inwards. 
In Iris each stamen stands under a petaloid style, which is pressed down 
upon one of the outer leaves or " fall." The style carries a small stigma 
just above the tip of the anther, at the base of the terminal flap. AYhen 
an insect forcibly enters between the fall and the style it gets dusted on 
the back, and if it have brought any pollen the inverted spoon-like style 
picks up the pollen, which is then lodged on the stigmatic ledge. In 
Gladiolus the three stamens, by bending the filaments, are all situated on 
the posterior side of the flower ; the anthers standing side by side and 
over-archiDg the tube, so that the insect visitor receives the pollen 
from all three at once. The extended overhanging stigmas then strike 
the latter where pollen has been deposited, i.e., brought from another 
flower. In Crocus the bee crawls head downwards by grasping the 
stamens and style, which together make a column in the middle. It thus 
receives the pollen on the abdomen. On flying to another flower it 
alights on the brush-like stigmas, which then sweep oft' the pollen. 
As another instance of mimetic forms. Crocus (Iridea^) resembles 
Stillingia ( Amaryllideie) and Colcliicum (Liliacea^). This same form of 
perianth has probably arisen from having been visited by similar insects 
in the same way. 
