42 



SCIENCE-GOSSIP. 



surface of its wings ; otherwise it is not a striking 

 insect, and what beauties it has are lost in drying. 



Agrion pulchellum, Linn., was taken occasionally 

 at the Black Pond, with the more plentiful A.puella, 

 from June 3rd till September. It was not common, 

 however, and being dark in appearance was easily 

 passed over. The bronze colour of its abdomen, of 

 course, does not fade. 



Agrion puella, Linn. It was far from as common 

 last season as sometimes. My records spread over 

 a period extending from June 3rd till September 

 19th. In 1893 it reached from May 14th till 

 September 24th. When living, this is one of the 

 most delicately beautiful of our dragon-flies ; but 

 with death, unfortu- 

 nately, all its beauties 

 entirely disappear. 



Pyrrhosoma minium, 

 Har., was out in large 

 numbers at the Black 

 Pond on April 29th, 

 and was on the wing 

 from that time till 

 about the end of June, 

 while I bred one on 

 May 4th from a nymph 

 taken from the same 

 pond. This and its 

 congener, P. tenellum, 

 make a pretty contrast 

 to their companion, 

 Agrion puella. The 

 crimson and bronze 

 colouring of both 

 species of this genus 

 are fairly persistent 

 after death. 



Pyrrhosoma tenellum, 

 De Vill. From June 

 23rd till August 7 th this 

 elegant little dragon- 

 fly was plentiful at the 



Black Pond, and seemed to take the place of its 

 somewhat larger and more robust congener when 

 that disappeared. 



Got don Road, Kingston-on-Thames ; February, 1895. 



The Geologists' Association. — The Easter 

 excursion of the Geologists' Association this 

 year, is to the Isle of Wight, under the direction 

 of Messrs. R. S. Herries, F.G.S., and H. W. 

 Monckton, F.G.S., leaving London on April nth, 

 and returning on the 16th. There are four 

 excursions arranged for different days, the localities 

 being — (1) walk to Whitecliff Bay, (2) Alum Bay, 

 (3) Totland Bay, (4) Coast from Seaview to Ryde. 

 Full particulars may be obtained from Thos. 

 Leighton, Esq., Lindisfarne, St. Julian's Farm 

 Road, West Norwood, S.E. 



Daisy. — Bcllis 

 Fig. 1. 



STATIONS OF PLANTS AND 



BUOYANCY SEEDS. 



By H. H. Guppy, M.B. 



DY following up the path of inquiry that is 

 concerned with the flotation of seeds and 

 seed-vessels, we are guided into other fields of 

 research that give promise of interesting discoveries 

 in connection with plant-life. We are led, in the 

 first place, to consider the question of utility, and 

 to ask whether the buoyancy of the seed or fruit 

 has been a matter of moment in the history of the 

 species. Nature is ever engaged in telling off the 

 plants to their various stations. She places the 

 yellow iris at the river's 

 side, and assigns to the 

 blue iris its home in a 

 shady wood. Under 

 her direction the com- 

 mon alder thrives at 

 the water's edge, whilst 

 its fellow species live 

 on the mountain slope. 

 These and similar oper- 

 ations are carried out 

 daily around us, and 

 we know but little of 

 the wherefore and the 

 how. We are induced, 

 therefore, to inquire 

 whether by pursuing 

 the line of investiga- 

 tion above indicated we 

 may be able to get a 

 glimpse at the methods 

 adopted by nature in 

 selecting stations for 

 plants. 



I possess the results of 

 buoyancy experiments 

 on the seeds of about 

 273 British plants. Of 

 these about 230 plants are included in my own 

 results, whilst the data for the remainder have been 

 obtained mostly from the writings of Kolpin 

 Ravn, Thuret and Darwin. The term " seed " is here 

 used in its general sense, and it should be added 

 that the greater density of sea-water as compared 

 with fresh-water makes, as a rule, little or no 

 difference in the experiments. Of the total number 

 of species the seeds of 210, or seventy-seven per 

 cent., sank at once or within a week ; in thirty-five 

 species, or thirteen per cent., the seeds floated in 

 numbers after six months in water, the remainder 

 floating for periods usually of two or three months. 

 No doubt, if the grasses had been better represented, 

 the proportion of those that sink at once or within 

 a week would not have been under ninety per cent. 

 That seeds as a rule possess but little buoyancy 



perennis. Mons. 

 (See p. 44.) 



