200 



SCIENCE-GOSSIP. 



none dropping more than two feet away. The 

 seeds, although they will float on smooth water, 

 sink at a touch. Though this plant is doubtless 

 indebted to aquatic fowl for the transportal of its 

 seeds across the ocean to Kerguelen and Bermuda, 

 it probably owes its wide distribution in all the 

 continents to the refuge it has always found during 

 revolutionary epochs beside the perennial spring. 



Hypericum elodes has a curious method of propa- 

 gating itself from the detached extremities of the 

 stems and branches that float, through the winter, in 

 the seed-drift of the pond. In the middle of winter 

 the beds of this plant are to be observed mostly 

 dead and entirely submerged. The terminal buds, 

 however, retain their vitality, and as the plant 

 decays, the ends of the stems and branches become 

 detached and float up, a process often assisted 

 by the ice. These detached extremities, which 

 are from a quarter to one inch in length, are to be 

 found floating in numbers during spring. They 

 assume the vertical position, the terminal bud 

 uppermost ; and when the bud expands, the young 

 leaves protrude a line or two above the surface of 

 the water. Like the water-spider that abounds in 

 this pond, the young leaves of the opening bud 

 exhibit in a remarkable fashion the properties of 

 the surface-film, a subject made familiar by the 

 illustrations of Professor Miall. They cannot be 

 wetted, and when pushed under reappear before 

 long with their surfaces perfectly dry. As the 

 spring advances these floating portions grow in 

 length, and when about two inches long they pro- 

 ject half an inch above the water, roots being 

 developed from the submerged nodes. Since the 

 seeds sink, this is the only means of dispersal by 

 water possessed by this plant. 



In propagating itself in the spring from free- 

 floating portions of the plant, Hypericum elodes 

 follows much the same method which I described 

 in this journal in the case of Ceratophyllum demersum 

 (Science-Gossip, vol. i., N.S., p. 195). Other 

 aquatic plants reproduce themselves in the spring 

 from buds that float through the winter. This 

 is notably the case with Hydrocharis morsus-rana, 

 its buds floating in numbers at the surface of 

 the Wanstead lakes. Kerner gives a beautiful 

 illustration of these Hydrocharis buds. He im- 

 plies that they pass the winter at the bottom. I 

 find, however, that a good proportion never sink. 

 Triglochin palustre in the ditches of Bushey Park, 

 behaves in a similar manner. The plant there 

 produces slender fugacious stolons terminating 

 in buds, which float throughout the winter and 

 propagate new individuals in the spring. These 

 buds are freed by the death of the delicate 

 stolons as winter approaches. Neither in Syme's 

 work, nor in De Candolle's " Monograph. Pha- 

 nerog" (1881), do I find these buds referred to. 

 On account of the lack of buoyancy of their fruits 



or seeds, the floating buds of Triglochin palustre 

 and Hydrocharis morsus-rana alone furnish these 

 plants with the means of dispersal by water. (See 

 Kerner, Engl. edit. ii. 810, on the Transportal of 

 Triglochin Carpels in Birds' Plumage.) 



Much interest also attaches itself to the seed- 

 drift of the Black Pond, which, as it floats on 

 the surface from the autumn to the spring, 

 affords information as to the buoyancy of the 

 seeds and fruits of the plants of the pond. We 

 do not observe here the fruits of Eriophorum 

 polystachion or the seeds of Viola palustris ; and 

 experiments show that they possess little or no 

 floating powers. We find throughout the winter 

 numbers of the floating fruits of Hydrocotyle vulgaris 

 and of Potamogeton oblongus, together with the 

 grains of Arundo phragmites, all of which can float 

 for many months. This last-named plant is one of 

 the very few amongst our hundred species of 

 grasses that have grains with any buoyancy worth 

 speaking of. Nature performs a grand flotation 

 experiment in the seed-drift of our ponds and 

 rivers, the grasses being scarcely represented. 

 Even the grains of Poa aquatica and Leersia 

 oryzoides, which, from their station, we might have 

 expected to display floating powers, sink, accord- 

 ing to M. Kolpin Ravn, after a few days. 



In the floating seed-drift of the Black Pond we 

 have that of a pond lying in a boggy district, and 

 mostly isolated by its elevation from surrounding 

 drainage areas. Ponds in low-lying regions, com- 

 municating directly with rivers and fed by their 

 tributaries, resemble rivers closely in the character 

 of their drift. There we find, floating in numbers 

 through the winter to the spring, the fruits of 

 Ranunculus sceleratus, Bidens sp. sp., Lycopus 

 europaus, Scutellaria galericulata, Alnus glutinosa, 

 Sparganium ramosum, Iris pseudacorus (seeds), etc., 

 etc., with duckweed, bulbs, buds, and, amongst 

 miscellanea, the bulbiferous leaflets of Cardamine 

 hirsuta and C. pratensis. This matter is treated 

 with more detail in a short paper I contributed in 

 1892 to the "Journal of the Linnean Society." I 

 would recommend anyone interested in this 

 subject to collect a quantity of river-drift in 

 November and keep it floating in a bowl until the 

 spring. The young naturalist will find here a 

 multitude of things to exercise his observing 

 powers. He need not be acquainted with the 

 name of a single seed ; but when they germinate in 

 his bowl in the spring, he can put them in soil and 

 raise the plant, and where this is not possible he 

 will find an object of many a ramble in his search 

 for the parent plants. 



One curious feature in this pond is to be found in 

 the abundance of caddis-worms and the consequent 

 absence of duckweed (vide March, 1895, anie P- IX )- 



6, Fairfield West, Kingston-on-Thames ; 

 September, 1895. 



