June 12, 1886 
THE GARDENING WORLD 
645 
Epidendreje!. 
The pollinia here are either free or united by short 
caudicles. Dendrobium is typical of the first state and 
has generally four waxy pollen masses, in two closely 
applied parallel pairs. The labellum of Dendrobium 
nobile, Falconeri, Aureum, Pierardi, infundibulum, 
and numerous others, is curved round the column so 
as to form a tube for the reception of correspondingly 
large insects, which when retreating, push off the 
anther-cap and at the same time have the pollinia 
glued to their bodies, by means of the viscid matter 
forming part of the rostellum. The pollinia instantly 
fall down flat on the insect, a little nearer or towards 
its head, so that a visit to the next flower brings the pol¬ 
linia in contract with the viscid stigma, where they are 
retained. This action is further assisted when the fila¬ 
ment of the anther is elastic, as frequently happens, and 
serves toscoopoutthepolliniabyreversing theanthercap. 
The other type of this tribe is represented by 
Coelogyne cristata, where the four pollen masses cohere 
in pairs subtended by short appendages or caudicles 
that connect them with the viscid matter of the ros¬ 
tellum. As far as fertilisation is concerned this differs 
immaterially from the former case. In this particular 
species the pollinia are much shorter than the rostellum, 
and cannot be removed by an insect entering the flower. 
A large insect when retreating would lift up the 
rostellum, which in its turn would press against the 
anther, and that meeting with resistance from a broad 
membraneous hood-like expansion behind it, the pollinia 
are shot or pushed against the retreating insect, to 
which they are glued and transferred to the stigma of 
the next flower visited. The five lacerated lamellae or 
coarse fringes along the middle or floor of the labellum 
offer considerable obstruction to retreating insects, 
causing them to brush against the rostellum in the 
manner described. 
Vande.k 
The members of this tribe are characterised by a very 
high development of parts, and many beautiful and 
perfect co-adaptations between them and the insects. 
The pollinia possess caudicles, attached to pedicols and 
those again to a viscid gland reesmbling or comparable 
to a foot. The pedicel is an unmodified layer of the 
rostellum, and the gland also belongs to the same organ. 
By an extraordinary twisting of the ovary, the label¬ 
lum in Angnecum eburneum is iqipermost, at least, 
during'the period of fertilisation. This is necessary 
owing to the length and direction of the nectary in 
order to keep its mouth upwards and prevent loss. 
The short stout column with its broad bifid rostellum 
offers the most convenient landing place for insects. 
The pollinia would attach themselves to the underside 
of an insect’s head, and dangling down, by their own 
weight would be retained by the viscid disk of the next 
flower visited, or actually wrenched away from the 
insect by the clefts of the rostellum. 
The process is very different in A. citratum, in which 
the pollinia possess very long slender pedicels. A smaller 
insect fertilises this species, and the slightest touch 
removes the pollinia from the anther, when the elastic 
pedicels contract or double up instantly in an irregular 
manner, fixing the pollinia themselves close to the gland 
on the head of an insect in the immediate vicinity of the 
stigmatic disk. The labellum forms the landing stage 
in this species. The pollinia in Phalsenopsis, Odonto- 
glossum and Oncidium when attached to the head or 
proboscis of an insect are brought into the proper posi¬ 
tion, to fertilise the next flower visited by a hygrometric 
depression of the lower half of the pedicel, and a curva¬ 
ture of the upper. This takes place with remarkable 
precision in from thirty to forty seconds. The pollinia 
after this movement project upwards at an angle calcu¬ 
lated to catch the stigma of the next flower visited. 
Neottiete. 
The pollinia in this tribe consist of granular or pow¬ 
dery easily broken masses fastened together by elastic 
threads attached to the back of the rostellum, part of 
which in front is modified into a linear gland. The 
caudicle and pedicle present in the last tribe is here 
absent. Spiranthes autumnalis, a British species, may 
serve as a type. The small labellum stands erect against 
the column forming a narrow tube. Its upper part is 
recurved and crisp at the margin, affording a foothold to 
insects, in this case humble bees. These inserting their 
proboscis in the narrow tube, effect the removal of the 
pollinia with beautiful regularity, by means of the linear 
gland on the face of the rostellum. Older flowers only 
are fit to receive the pollinia, and the bee in visiting the 
next plant finds it convenient to begin at the lower 
part of the spike where the flowers are oldest, and 
working upwards. 
Ophkydeie. 
The greater number of British species belong to this 
tribe ; but all the tribes are represented by British 
types except the Vandse. The pollinia in Ophrydeae 
consist of large compound masses made up in coarsely 
granular packets, and held together by elastic threads 
united to a viscid gland or glands by more or less 
elongated caudicles. Several species of Orchis, such as 
0. morio, mascula, latifolia, and maculata, are fertilised 
in a similar way, and any will serve as a type of the 
tribe, although it must be understood that none of the 
above types represent in detail what takes place in other 
members of the same tribe. They merely represent in 
general terms the bearing that the different kinds of 
pollinia have on the process of fertilisation. The glands 
of the pollinia in Orchis maculata are contained in a 
pouch shaped rostellum projecting into the orifice of the 
nectary. The structure of the flowers compel the insects 
(generally bees) that frequent them to insert their 
proboscis in a particular way, depressing the pouch 
when the adhesive glands fix the pollinia to the head 
of the insects, and ensure their removal with remarkable 
precision. The hygrometric movement of depression 
noticed in the pedical of some members of the Van die, 
is here confined to the upper surface of the gland itself, 
and is completedin the courseof half-a-minute, bringing 
it down parallel with its point of attachment, and in a 
position to strike the stigma of another flower. Lepi- 
doptera fertilise the British species of this tribe with 
long nectaries. 
Cypripedie.e. 
The pollen of this tribe, unlike any yet mentioned, 
is perfectly free, representing a former and much simpler 
condition of the order. It is produced in two lateral 
anthers belonging to an inner series of three, and 
the separate grains are coated with viscid matter by 
■which they are retained on the convex stigma. The 
pouch-shaped labellum is constructed so as to compel 
insects that enter by the large trap-like opening, to 
leave by two small lateral and basal openings, thus 
leading them over the concealed stigmatic disc and 
afterwards the anthers. The extreme base of the 
labellum internally and the base of the petals skirting 
the narrow openings are in many species densely 
bearded or beset with hairs, offering further obstruction 
to the egress of insects, except over the stigmas and 
anthers. In Cypripedium venustum the convex surface 
of the dry stigmatic disc is obsoletely papillose, but a 
fringe of distinct papilla; round the margin, doubtless, 
aids the retention of the viscid pollen grains. This 
condition applies very closely to many other if not all 
the species belonging to tropical Asia and the East 
Indies, as C. concolor, Godfroyse, insigne, javanicum, 
Spicerianum and others of the same group. The same 
organ of the South American subgenus Selenipedium, 
including Uropedium, is distinctly papillose all over, in 
S. longiflorum, conchiferum, Roezlii, and many others, 
thus furnishing another mark of distinction between 
them and Cypripedium proper, besides the three celled 
ovary and native country. The lateral sepals are com¬ 
pletely united in these genera, forming a support to the 
labellum, except in Cypripedium arietinum, where they 
are almost free, representing a more primitive condition 
of the tribe. 
Objects of Ijcsect visits. 
We have no reason to suppose that insects are in the 
slightest degree conscious of the great benefit they 
bestow on Orchids by effecting cross fertilisation. The 
sole object of their visits is for their own material 
benefit, namely, food or a means of subsistence. The 
beautiful co-adaptations that exist between them and 
