222 NATURAL SCIENCE. April, 



with another excellent teaching exhibit, illustrating the methods of 

 dispersal of fruits and seeds. 



In many cases scattering of the seed, often over a considerable 

 area, is ensured by the structure of, or certain mechanism in the 

 fruit capsule itself. Elasticity of the dried walls is a common agent. 

 Many pods for instance split suddenly, the two halves twist spirally, 

 thereby jerking out the seeds which lay in a row on their inner 

 surface. The capsule of the violet forms on dehiscence a three-rayed 

 star, each ray bearing the small roundish seeds in its concave upper 

 portion, the edges of which gradually close together and shoot out 

 the seeds. Sir John Lubbock stated that they sometimes fall several 

 yards from the parent plant. The Impatiens which has taken 

 possession of our gardens in recent years, is an admirable instance 

 of the success of this device. Here the strips of the lateral walls 

 of the fruit corresponding to each carpel, are at maturity in a state 

 of longitudinal tension. Ultimately the weak place at the base gives 

 way, and the walls curl elastically upwards, each strip slinging its 

 seeds out with considerable force. In the closely allied genus 

 Geranium the same principle holds, the outer walls of the carpel when 

 ripe springing backwards and upwards from the central column. 

 In Hura crepitans, the sand-box or monkeys' dinner-bell, a tropical 

 American ally of our native spurges, the woody fruit explodes with 

 a loud report by the sudden separation of the individual carpels from 

 the centre, and the flat seeds are shot out. Other fruits and seeds 

 are water-borne. The wide distribution of the coco-nut palm 

 through the islands of tropical seas is thus accounted for. The 

 fibrous husk forms the float, and its tough leathery outer layer keeps 

 out the sea-water. When thrown up on the beach the seed 

 germinates, the embryo growing out through the soft round spot at 

 the end of the hard nut-like inner wall of the fruit. The three spots, 

 like the three longitudinal lines in the wall, are relics of the time 

 when there were three chambers to the fruit each with its seed, 

 instead of a single one as at present. 



The Nipa is another palm which is distributed in the same 

 way. It grows along muddy shores and brackish estuaries from 

 Ceylon to New Guinea. The fruits are crowded in a large round 

 head as big as a cannon ball ; when ripe they separate and fall into 

 the mud or water, and having a thick light fibrous coat will float and 

 may be carried a long way by currents. In his Himalayan Journal, 

 Sir Joseph Hooker refers to the large numbers turned over by the 

 paddles of his steamer at the mouth of the Ganges. The seeds of a 

 widely distributed tropical bean, Entada scandens are often carried by 

 the Gulf stream, and thrown up on the Western shores of our 

 islands and of Norway, where they will germinate. Ages ago, 

 they were floating round the estuary of the Thames, and along our 

 southern coast, where they are found to-day as fossils along with 

 other estuarine organisms which go to show that their habitat in 



