292 



Garden and Forest. 



[Number 492. 



states that sheep-herding should be forbidden in all the 

 national forests. In the" face of this the Administration 

 permits it in two states, and thus takes the responsibility of 

 endangering- the interests of large communities. Nobody- 

 knows what sort of pressure has been brought by these 

 two states to exempt them from restrictions imposed upon 

 other reservations, but certainly the pasturage of these 

 great ranges, although it may help to enrich a few indi- 

 viduals, is against the highest welfare of the people of the 

 United States, who own these lands and the forests on them. 



The Douglas Spruce. 



THE illustration on page 295 of this issue gives a far 

 better idea of the dimensions attained by this tree 

 than any mere enumeration of diameter measurements. In 

 the region adjacent to Puget Sound, where the logs repre- 

 sented in our illustration were cut, the Douglas Spruce, 

 Pseudotsuga taxifolia, grows to its largest size, often attain- 

 ing a diameter of ten feet above the swell at the base of the 

 trunk. Trunks twelve feet in diameter are reported, but if 

 they exist they are very rare, trees with stems five or six 

 feet in diameter representing an average good forest 

 growth. The maximum height which this tree attains is 

 still doubtful, and we shall be glad of any facts regarding 

 it. It is probable that some specimens near Puget 

 Sound have grown three hundred feet high, and there 

 are stories, still needing confirmation, of individuals 

 four and even five hundred feet in height. So far 

 as we know, however, the tallest North American tree 

 of which there are reliable measurements is the Redwood, 

 measured last year on Eel River, California, by Professor 

 Sargent, General Abbot and Mr. John Muir (see vol. x., p. 42), 

 which was three hundred and forty feet in height. 



The Effects of Wind on Trees. 



THE great tornado of May 27th, 1896, gave an oppor- 

 tunity rarely offered for observing the effects of a 

 strong wind on different trees. Professor J. B. S. Norton, 

 botanical assistant in the Missouri Botanic Garden, took 

 abundant notes at the time and has watched the trees dur- 

 ing the past winter and marked their growth this spring. 

 The results of these observations were embodied in an 

 interesting paper read before the St. Louis Academy of 

 Science, the chief portions of which we take pleasure in 

 presenting to our readers through the kindness of Professor 

 Norton : 



The general effects of wind on trees play no very important 

 part in the economy of nature. The action of varying winds 

 on trees calls forth the efforts of the trees to strengthen the 

 wood in every direction, so that trees growing in exposed sit- 

 uations are stronger and consequently make better lumber. 

 The only thing to keep whole forests from being overthrown 

 where the trees are crowded together is the protection afforded 

 by the more sturdy ones on the border. In localities where 

 there is a prevailing wind the trees lean in the opposite direc- 

 tion, as is noticeable along the seacoast, where they seem 

 to grow away from the water. Mr. Eigen, in Zoe, April, 1892, 

 says that, besides causing the phenomenon just mentioned, 

 the wind plays a prominent part in determining the shape of the 

 tree. Most trees in wind-swept places have horizontal crowns. 

 Some of these may grow more erect when transplanted to 

 other situations. One species of Baccharis on the coast of 

 California, with a spreading top, changes its shape so much 

 when grown in the mountain regions away from the wind that 

 the mountain form has been described as a different species. 

 Other species that have grown for ages in windy situations may 

 have the horizontal shape so fixed that it is retained wher- 

 ever they may be grown. 



In looking over the trees about St. Louis most of my obser- 

 vations have been confined to the western part of the city near 

 the Missouri Botanical Garden and Tower Grove Park, where 

 the damage was done by a straight wind trom a westerly 

 direction. This is shown even now by the fact that most of 

 the branches removed were from the west side of the trees, 

 where they were bent more by the wind, those on the oppo- 

 site side being under but little transverse strain. A great 



many trees that were partially uprooted are still inclined more 

 or less toward the east. A few trees that were strained beyond 

 the limit of the elasticity of their trunks, and yet did not break, 

 still retain the curve away from the wind. This can be seen in 

 a few Taxodiums in the garden and in many Elms about the 

 city, perhaps in other trees. In Lafayette Park, where the 

 genuine tornado did its work, the conditions are quite dif- 

 ferent and the destruction much greater, but many things 

 besides wind must be taken into account as causes of the effects 

 observed. Soil conditions have much to do with the uproot- 

 ing of trees, as also does the root-form. Trees like the Spruce, 

 with spreading: roots near the surface, will be much more 

 easily uprooted than those with tap-roots. If the root system 

 and the soil which surrounds it is able to stand more strain 

 than the parts of the tree above ground a break in the trunk 

 or branches will result. The breaking depends on the strength 

 of the wood, the amount of surface exposed to the wind by 

 branches and foliage, and to a great measure on the shape 

 and position of the tree and the method of branching. Coni- 

 cal trees like the Sweet Gums, European Elms and most of 

 the conifers would have less strain on the roots and trunk than 

 those of the opposite shape like American Elms, and Maples. 

 The latter have the most of the wind exposed surface toward 

 the top where the wind is stronger, and the additional force 

 and weight so far from the base gives a greater leverage on 

 the roots and trunk. So we should expect more of the spread- 

 ing-topped trees to be broken or uprooted, and such is the 

 fact. But the breaking or splitting of so many trees of this 

 form is to be attributed more to their method of branching. 

 Trees with excurrent trunks and small lateral branches are not 

 nearly as apt to be broken as those with a number of large 

 ascending branches. Tf ees of great elasticity would be injured 

 less than those not so elastic. The Silver Maples suffered as 

 they did probably on account of their brittle wood, not being 

 able to give before the wind without breaking, like some 

 more elastic woods. 



The damage would have been much less had the tornado 

 made its appearance when the trees were leafless. Taking all 

 the wind storms together, the coniferous trees are probably 

 injured more than others for the reason that they always have 

 a heavy load of leaves and because most of the wind storms 

 come when the deciduous trees are leafless. The leaves offer 

 a much greater surface for the wind to play upon, and espe- 

 cially do wet leaves, as has been pointed out by Mr. Kerr in the 

 Proceedings of the Staten Island Natural Science Association 

 for March, 1895. Where the leaves are not matted together by 

 the water in rain storms, as they probably were in the St. Louis 

 tornado, and thus offer more weight and resisting surface to 

 the wind, it is interesting to notice what a small surface they 

 present. The petioles are flexible in many trees, like the 

 Maples, and especially the Poplars, and in the wind they allow 

 the leaf-blade to assume a position parallel to the direction of 

 the wind, thus presenting to it only the edge. The Silver 

 Maple probably suffered more from the storm last May than 

 any other trees. Scarcely a tree touched by the storm is 

 left unbroken, and most of them have lost the principal 

 branches or even the whole crown. The trees are well rooted, 

 and the brittle wood, with its mass of foliage, is easily snapped 

 off. Ulmus Americana suffered principally because the heavy 

 spreading top with its slender branches is in such a posi- 

 tion that they were easily split off. The irregular growth of 

 the fibres makes the wood very tough, though it is only mod- 

 erately strong. Where no weakness in the structure of the 

 trees exposed them to injury, this species has withstood the 

 storm remarkably well. In Lafayette Park, where everything 

 else was almost totally destroyed, some Elms, full of branches, 

 remain standing, though in many cases the branches are bent 

 out of their original position. Trees of Liriodendron Tulipi- 

 fera, in consequence of their weak brittle wood, were broken 

 off through the main trunk. The Basswood suffered in about 

 the same way. The Osage Orange of our hedges has very 

 strong, tough wood, but the results of the storm show that it is 

 easily split and uprooted. The large leaves, as well as a poor 

 root system, allowed manyCatalpas to be uprooted. The wood 

 is not strong, but the number of branches partly twisted off 

 shows that it is not so easily broken as some stronger woods. 

 The Oaks are among the strongest woods, and were scarcely 

 injured. Most of the Oaks are as well able to withstand wind 

 storms as any trees we have. The trunk is excurrent and the 

 gnarly lateral branches are very thick and strong. The trees 

 are also very well rooted. Many trees of Populus monilifera 

 are stiil standing about the city, though this tree has weak 

 wood and grows so rapidly that it is little protected by other 

 trees. Ulmus campestris and Liquidambar Styraciflua were 

 little injured. Their salvation was in their form, a strong 



