A NEW THEORY OF FLORAL STRUCTURE. 9 
of plants called “protoplasm” is this, that it is extraordinarily 
sensitive to all kinds of stimulants, such as heat, light, air, 
water, chemical substances and also mechanical irritations. 
The last is the one specially concerning us now. We know that 
a merely mechanical touch of a stick will cause the tendril of a 
Pea to twist round it ; that a rough wall induces the slender 
tendrils of the Virginian Creeper to develop little adhesive pads 
and then to thicken and twist as well; that the leaf-stalk of 
a Clematis twists round a support and at once develops a 
quantity of woody tissue in consequence. These and many 
other instances show that growth can be made to take place in 
response to mechanical strains and forces brought to bear upon 
plants. Now apply this to flowers, and similar or analogous 
effects are seen. The insect has to alight. If it have to rest 
on a flower, the latter must accommodate it. This it does by 
enlarging the lip, &c. At the same time it secretes honey just 
where the insect sets up an irritation by probing for juices. 
If we thought the flower made the honey-glands in anticipa- 
tion of an insect coming, we should fall into the old mistakes of 
what is called Teleology. Hence there is no alternative but 
that the insect itself is the direct cause of the secretion.* 
It would take too long to furnish all the facts and reasonings 
to support this view, that all flowers adapted to insects have 
assumed their present forms through what may be called the 
“ Responsive power of Protoplasm ” on the one hand, and the 
“ Direct Action of the forces of the Environment,” using the 
term in the widest sense, on the other. 
Conversely, those flowers which, from some reason or other, 
such as migration, are no longer visited by the particular insects 
which attended them, or have found an inclement climate, or 
have degenerated in structure ; they no longer develop honey, 
they reduce the useless expenditure of too many stamens, and 
place the anthers in direct contact with the stigmas of the same 
flower. They thus become perpetually self-fertilising ; such are 
the Knotgrass ( Polygonum aviculare), Shepherd's Purse ( Capsclla 
Bursa-pastovis), varieties of Chickweed ( Stellaria media), &c.t 
The reader must understand that these few cases of adapta- 
tions in the vegetative organs of plants and in their flowers are 
but hints, as it were, of the vast number of facts which, taken 
together, offer an accumulative evidence which is forthcoming 
when we study plants, especially in relation to their environ- 
ments ; so that the conclusion is forced upon one that all kinds 
of structures which are in adaptation to the environment have 
been brought into existence by the plant responding to it ; that 
* It might be suggested that flowers spontaneously vary in all sorts of ways, 
and that those best adapted to insects only survive ; but there is no evidence in 
support of this idea. It therefore remains an a priori assumption only, without 
any verification. 
f The reader will find the whole subject treated in The Origin of Floral 
Structures, International Science Series, No. 63. 
