106 JorilNAL OF THE K<)YAL II( >liTICULTUIlAL SOCIETY. 
THE DISPERSAL OF SEEDS. 
By G. S. BouLGEE, F.L.S., F.G.S., Professor of Botany, 
City of London College. 
llead July 25, 1899.: 
Every agriculturist and every gardener is familiar with many of the 
results of the dispersal of plants — dispersal to small and dispersal to great 
distances. The weeds in our gardens are, it has been said, merely plant- 
out of place, which have often not travelled very far — perhaps only from 
the land of a slovenly neighbour — to reach an open space. We often find, 
on the other hand, that two species of some one genus that we cultivate 
may have come from regions widely removed from one another, or that 
the area of distribution of a single species may be of vast extent. 
After having, by the exercise of its nutritive functions, attained to 
maturity, the one physical object of every organism is the perpetuation of 
the species. This, as is so generally the case in organic nature, is an end 
effected by many diverse methods, which may well be classed roughly into 
the two heads of vegetative and sexual. To the former class— in the 
vegetable kingdom — belong " innovations," rhizomes, bulbils, tubers, 
runners, offsets, suckers, proliferous leaves, besides many kinds of spores 
(among Cryptogams). Beyond remarking that, as these cases consist 
■essentially in the detachment of a shoot of the parent plant, the detached 
^'offspring closely resembles the one parent to which it owes its origin, 
we are not to-day directly concerned with them. It is, however, a matter 
of considerable interest to note, as showing the identity of the physio- 
logical requisites in all cases of dispersal, that we have in this class of 
lower or vegetative methods a foreshadowing, as it were, of almost every 
method of dispersal which obtains among fruits and seeds. For example, 
the extreme lightness of the spores of many fungi, of Lycopodium and 
of other plants, undoubtedly facilitates their dispersal by wind, as does 
the lightness of the seeds of some Orchids and of many parasites and 
saprophytes. The bin'sting of puft'-balls, the explosion under the influence 
of hygroscopic action of the annulus of the sporangia in Ferns, the threads 
of the capillitium in the Myxomycetes, and the elaters in Hepatic^, and 
the scattering of Moss-spores between the teeth of the capsule as it sways 
in the wind, similarly anticipate the cases of the Sandbox-tree {Hurn 
crepitans, L.), the Balsam {Inipatiens), the hairs in the capsule of 
Vanda teres, the "jaculators " in the fruits of Acanthacea?, and the so- 
called censer action " in a Poppy-head or in the fruit of one of the Pinks. 
So, too, water serves to carry the " hibernacula " or winter buds of 
Ilydrocharis as it has dispersed the fruit of the Cocoa-nut Palm ; wind 
rolls along offsets of some species of Sempervivum, as it does the globular 
fruit-heads of several species of Trifolium ; and flies carry the spores of 
the Stinkhorn {PJiallus wipiidicus) or the Ergot (Claviceps), and the 
higher animals the spinous offsets of Cactuses ; just as ants carry the 
seeds oi Chclidonium or Mclaiwpyrum, or the burr-like fruits of thousands 
of flowering plants are entangled in the hair of any passing animals. 
