130 



NA TURE 



[J2ine 7, 1888 



does occur at the margins of the wounds in the Alps 

 where the larch is native. In these higher region?, how- 

 ever, the air is usually dry during periods of active growth 

 and the young fructifications of the fungus are particularly 

 sensitive to drought ; consequently, even when many 

 scattered trees are infected, the cups developed at the 

 edges of the wounds are apt either to dry up altogether, 

 or to produce relatively few spores, and these spores have 

 fewer chances of germinating. In fact, the fungus enjoys 

 at best a sporadic existence, chiefly at the bases of trees 

 where the herbage affords a certain degree of dampness. 



When the larch was brought down to the plains and 

 valleys, however, and planted in all directions over large 

 areas, the Peziza was also brought with it ; but it will be 

 clear from the foregoing discussion that the climatic 

 conditions were now proportionally raised in favour of 

 the fungus, and lowered to the disadvantage of the larch. 

 Plantations in damp valleys, or in the neighbourhood of 

 the sea, or of large lakes, were especially calculated to 

 suffer from frost, and the damp air favoured the propaga- 

 tion of the fungus, and the disease tended to become 

 epidemic. The enormous traffic in larch plants also 

 shows how man too did his share in spreading the epi- 

 demic ; and in fact the whole story of the larch-disease 

 is of peculiar interest biologically, as illustrating the risks 

 we run every day in trusting to the chapter of accidents 

 to see us safely through any planting undertaking, no 

 matter how great the stake at issue, or how ruthless the 

 interference with those complex biological and physical 

 conditions which always play such an important part in 

 keeping the balance in the struggle for existence between 

 all organisms living together. 



Let us now very shortly see what are the chief lessons 

 taught us by the bitter and costly experience which the 

 larch-disease brought to foresters. It is evident that the 

 larch should not be planted at all in low-lying situations 

 exposed to late frosts ; and even in more favoured valleys 

 experience points to the advantage of mixing it with other 

 trees : large areas of pure larch are planted at enormous 

 risk in the lowlands. 



As to the treatment of trees already diseased, it is 

 possible (when it is worth while) to remove diseased 

 branches from trees of which the trunk and crown are 

 healthy, but it hardly needs mention that such diseased 

 branches must be burnt at once. As regards trees with 

 the stems diseased — in those cases where the patches are 

 large, and much resin is flowing from the wounds, ex- 

 perience points to the advisability of cutting them down. 

 In those cases where the tree is already very large, and 

 the diseased wound but small, it may be expedient to let 

 them alone : theoretically they ought to go, or at any rate 

 the diseased tissues be excised and burnt ; but it seems 

 to be proved that such a tree may go on forming timber 

 for many years before the wound will spread far enough 

 to reduce the annual increment below the limits of profit, 

 and we all know the view a practical forester will take of 

 such a case. At the same time, it is the duty of the man 

 of science to point out that even such a tree is a possible 

 source of danger to its neighbours. 



H. Marshall Ward. 



( To be cofitinued.) 



MARINE BIOLOGY AND THE ELECTRIC 

 LIGHT. 



'THE Liverpool Salvage Association, with their usual 

 -■• liberality, placed their famous old steamer the 

 Hycena once more at the service of the Liverpool Marine 

 Biology Committee this Whitsuntide, for a three days' 

 dredging expedition. During the three former biological 

 cruises of the Hycena in 1885, 1886, and 1887, the region 

 explored has been the southern part of the L.M.B.C. dis- 



trict, around the coasts of North Wales and Anglesey 

 (see Fig.). 



On the present occasion the Committee decided to run a 

 couple of lines of soundings and dredgings between the 

 Mersey and the Isle of Man, and to spend some time 

 dredging round the southern end of that island ; the 

 general objects being (1) to get some knowledge of the 

 depths, bottom, and animals, across the eastern half of 

 the Irish Sea, and (2) to investigate the rich fauna living 

 around the '' Calf" and south end of the Isle of Man. 



About 7 a.m. on Saturday morning, May 19, the 

 Hycena left the Liverpool landing-stage, with a party of 

 nearly twenty biologists on board, and provided with 

 dredges, trawls, tow- nets, sounding-line, deep-sea reversing 

 thermometer, microscopes, and the other necessary instru- 

 ments, dishes, bottles, and reagents. After the well-known 

 sand-banks round the mouth of the Mersey had been 

 passed, soundings and bottom temperatures were taken 

 occasionally, and several times during the day a stop was 

 made for trawling, dredging, and tow- netting. A fair 

 amount of material, including some interesting larval 

 forms, was obtained, and for the most part preserved for 

 further examination. No greater depth than 23 fathoms 



Map of the L.M.B.C. District, showing the curse of the Hycena in 18 

 1886, 1887, and 1888. H, Hilbre Island ; v, Puffin Island ; f, Ramsey : 

 d, Douglas ; e, Port Erin ; c, the Calf. 



was, however, met with ; and there was nothing specially 

 noteworthy amongst the animals dredged, so far as could 

 be seen at the time. 



It had been intended to anchor for the night in Douglas 

 Bay, but during the dredging and trawling the vessel had 

 drifted so far out of her course that when evening came 

 it was found advisable to run for Ramsey. Here half the 

 party went on shore for the night, the rest staying on 

 board for the electric light experiments which will be 

 described further on. 



On the following morning an early start for the south 

 was made, and the rest of the party was picked up at 

 Douglas, and then the work of the day commenced. 

 The Hycena steamed slowly round the east and south 

 coasts of the island to Port Erin, dredging and tow-netting 

 at intervals, with very good results. When a stop was 

 made for collecting, the fullest advantage was taken of it. 

 The sounding- line and deep-sea thermometer were over 

 amidships, and two dredges, a large bottom tow-net and 

 one or more surface tow-nets, were put out astern. The 

 deep tow-net, devised and worked by Mr. W. S. McMillan, 

 was so weighted and buoyed as to work steadily at a 



