22 



HA RD WICKE' S SCIENCE- G OS SIP. 



Coloration in Plants. — The remarks of L G. 

 reminded me of a curious fact I noticed in connection 

 with some sprays of blossom from the everlasting pea. 

 They were early blossoms, of a gorgeous crimson 

 colour, and were used a good deal for table decora- 

 tion. When the cut flowers had been in water a day 

 or two, instead of drooping and falling, the stems 

 remained erect, but the highly coloured flowers 

 gradually changed in colour to a pale chalk-blue, to 

 much the same tint, in fact, as that of the hare- 

 bell. Nor was the colour one which gave the im- 

 pression as of a fading flower ; it was as though the 

 adopted colour was the natural and original one. 

 The change was noticed on some few occasions. 

 Blossoms taken later in the year did not, however, 

 change so well. — Edward A. Martin. 



Some Stray Plants in North London.— 

 Building is constantly in progress in suburban London, 

 and it often happens that when a large estate is laid 

 out for this purpose, only a small part is built on at 

 first, and the rest of the ground is left waste, often 

 for several years. As this neighbourhood is hilly, it 

 is often necessary to level the ground before building. 

 Whenever this is done, and the new surface left to 

 itself for any time, it is curious and interesting to 

 watch the plants that first take possession, together 

 with the common weeds. The following plants have 

 been noticed in such situations (with three exceptions 

 noted below) : Erysimum cheiranthoides, L., East 

 Finchley and Crouch End ; E. orientate, Br., Crouch 

 End ; Brassica tenuifolia, Bois., East Finchley and 

 Brickfield at Hampstead ; Camelina sativa, Crantz, 

 Muswell Hill and Crouch End ; Thlaspi arvense, L., 

 and Lepidium ruderale, L., Crouch End ; Dianthus 

 armeria, L., found once in a wood at East Finchley, 

 apparently indigenous ; Saponaria vaccaria, ! Crouch 

 End ; Impatiens parviflora, Hampstead, probably 

 brought with greenhouse refuse ; Melilotns officinalis, 

 L., and M. alba, Lam., Crouch End ; Potentilla 

 argentea, L., roadside, Plighgate ; Carum carvi, L., 

 Crouch End ; Centaurea cyanns, L., several locali- 

 ties ; Chenopodinm polyspermum, L., and Rumcx 

 maritima, L., Crouch End ; Panicnm viride, L., 

 Muswell Hill ; Phalaris canariensis, L., several 

 localities. None of the above are commonly found 

 about here, and none have gained a permanent 

 footing. They have appeared for two or three years, 

 and have then been choked out by the common 

 weeds. Where did the seeds of these plants come 

 from, and how were they brought ? It is not easy to 

 say, unless, indeed, they were brought with some of 

 the building materials that were used near. The 

 soil here is chiefly stiff London clay. — J. E. Cooper. 



Coloration of Flowers. — Let I. G. (page 

 281, Dec. number) rest assured that the colouring- 

 matters of the harebell and that of the gentian are, so 

 far as chemical reactions go, just the same. I have 



carefully examined the different parts of the harebell 

 (C. rotundifolia), with the result of finding the 

 quantity of pigment in the petals to be very small, 

 and their colour to be really not a pure blue, but 

 more or less purple. With regard to the gentian, it 

 is well known that the order to which it belongs is 

 specially rich in aromatic principles, calculated to 

 furnish a basis for the production of vivid and 

 brilliant pigments. The difference, therefore, in the 

 matter of stability, which these two flowers exhibit 

 on drying is, I think, solely to be attributed to the 

 relative quantities of the colouring-matters present in 

 the petals when they were put in the press, i.e., the 

 harebell with its small leaves contains very little, 

 while the gentian, with its abundant chlorophyllaceous 

 tissue and highly favourable habit, produces very 

 much more. Then again, that some gentians 

 gathered in Switzerland twenty years ago, should 

 now be as fresh as ever, is an extremely interesting 

 fact, inasmuch as it evinces how dependent the blue 

 and red tints of flowers are upon the brilliant and 

 prolonged sunlight of the alpine regions. Where, 

 on the other hand, as among the equatorial Andes, 

 there is almost perpetual fog and mist, nothing but 

 yellow flowers are produced. Finally, the fact of the 

 harebell being stained by an inner book-cover and 

 fly-leaf is nothing more remarkable than that of a 

 claret stain on an ordinary table-cloth or napkin. — 

 P. Q. Keegan. 



GEOLOGY. 



The " Underground Geology of London." — 

 The argument quoted by " Llesba " from Mr. Whita- 

 ker's important work on the above subject, is cer- 

 tainly a strong one in favour of deciding the age of 

 the doubtful red and grey beds as triassic. The 

 last edition of the book was in the press at the time 

 of the discovery of coal at Dover, and consequently 

 did not take cognisance of that fact. The remarks, 

 therefore, which Mr. Whitaker made in his paper 

 before the Society of Arts on April 23rd, 1890, were 

 made subsequently to the writing of the passage 

 which was quoted, and in this paper was the follow- 

 ing. " A few years ago there seemed to me to be a 

 balance of probability in favour of the new red, but 

 I now fear the balance has veered round, for some of 

 these red and grey beds at Streatham are more like 

 old red, or to the passage-beds from that formation 

 into the underlying Silurian, than to anything else." 

 It is well to bear in mind, that at a depth of 1255 feet 

 " some small objects, believed to be first remains, 

 occurred " in slightly differing sandstone to those 

 above, while in the last two feet (1257 feet and 1258 

 feet), the rock was " a hard grey micaceous sand- 

 stone containing carbonaceous fragments." — Edward 

 A. Martin. 



