INTRODUCTION. 87 
species. This arrangement is most probably correlated with the habits 
of the insect which effects its fertilisation. Ihave never been fortunate 
enough to find the insect, which may be some night-moth, though the 
colour of the flower is rather dingy, and it has very little scent. On 
the other hand, I have failed to find any nectar in its galea, or in the 
pouches of its side sepals; it may, however, be present in the surface- 
tissues. Whatever the method, it appears sufficiently effective, since 
it is a common plant, appearing very regularly every year, the 
individuals mostly scattered, but sometimes growing closer together 
and in some abundance along mountain streams. 
Disperis villosa.—The fertilisation of the flowers in this species 
appears to be but slightly more frequent than in D. Capensis. I 
examined 108 flowers gathered on 16th, 17th, and 18th Sept., 1884. 
Of these 28 had been visited by insects, and 8 had been fertilised. The 
following exhibits the details :— 
Both pollinia in situ ...... 81 stigmas pollinated ......... 6 
One pollinium removed... 17 ol Be Pet SEs che i 
Both pollinia removed ... 5 J eee eee 1 
Pterygodium catholicum.—In Sept., 1884, I examined 55 flowers 
from 16 different plants. Of these 16 had been visited by insects, 
15 had one or both pollinia removed, while 5 had been fertilised. 
There are, however, grounds for suspecting that some Orchids 
have, perhaps by the dying-out of the species of insect which is alone 
fitted to effect fertilisation, ceased, or are gradually ceasing, to 
perpetuate themselves by seed, and are now propagated by new 
annual tubers only. This was suggested by a writer in ‘Trimen’s 
Journal of Botany,’ vol. v. (1876), p. 251, in regard to the Orchids of 
Australia, which, he thinks, may be ‘in a special condition, inasmuch 
as energy is now being directed towards vegetative as opposed to 
sexually reproductive existence. This is evinced by the wonderful 
development of tubers and roots, some of which latter organs, we 
believe, may possibly be found to be modified leaves.” 
So long ago as 1863, Mr. Roland Trimen, F.R.S., contributed to 
the Linnean Society a note on this subject, so far as it is illustrated 
by the life-history of Disa grandiflora, which was published in the ‘ Lin- 
nean Society’s Journal’ (Bot.), vol. vii. (1864), p. 144, with an excellent 
drawing. He observes :—‘‘ When I examined the plants, most of the 
flowers were partially withered; but in the greater number, even in 
those quite withered, both pollinia were still in their cases; in not one 
instance had both been removed ; but in several flowers one had been 
carried away. In some of the withered flowers the pollinia protruded 
