January 31, 1890.] 



SCIENCE. 



67 



of a spring that becomes more rigid as it is extended or com- 

 pressed out. of its normal shape. My friend Thomas Meehan in- 

 forms me (Dec. 17, 1889) that he has "observed a case where the 

 interior hollow makes an annual layer of bark equally with the 

 exterior, ' ' and he is of the opinion that ' 'it is by the decay of 

 the outer layer of this inside course of bark after several years 

 that the knob becomes hollow. ' ' If this habit is general, it is an 

 admirable means of forming and of preserving undecayed, at the 

 smallest cost to the tree, a living elastic strengthener at the fork- 

 ing of the roots Wlien in a hun-icane the gi-eat ti-ee rocks back 

 and forth on its base, and with its immense leverage pulls upon 

 this odd-shaped wooden anchor, instead of straightening out in 

 the soft material, as an ordinary root might, thus allowing the 

 tree to lean over and add its weight to the destructive force of the 

 storm, it grips the sand as the bower-anchor would do, and re-" 

 sists every motion. The elasticity at the point of junction allows 

 one after another of the perpendicular flukes attached to the same 

 shank to come into effective action, so that before being drawn 

 from the sand or ruptured the combined flukes present an enor- 

 mous resistance. 



The di-awing opposite I have made for the purpose of simplifying 

 the discussion. It shows an hypothetical cypress with two roots 

 of the same length and diameter, — one with knees, the other 

 without them. The superior strength of the stifliened root would 

 seem sufficiently evident; but, with the view of obtaining the 

 judgment of a mind thoroughly trained in questions of this 

 nature, I submitted the drawing to my friend, Charles Macdonald, 

 late director of the American Society of Civil Engineers, whose 

 eye has been accustomed to estimating the value of strains in 

 structures by an active experience of twenty-five years, and who 

 has just finished the largest drawbridge in America, at New Lon- 

 don Mi. Macdonald ageeed with me that the root B, which is 

 trussed with the knees C and C, would very largely exceed in 

 capacity for holding the tree firmly in yielding material the root 

 A, which is similar but destitute of knees. This greatly in- 

 creased .security against desti-uotion by storms is, I think, a suf- 

 ficient advantage to account for the existence and maintenance 

 of an organ that draws so slightly upon the vitality of the 

 plant. 



It is proper to record here another observation that may explain 

 the existence of the elevated, narrow point which the knee some- 

 times develops, and which rises higher than the curved grovi^th 

 that would be necessary to secure the maximum resistance to 

 compression and extension. The home of the cypress is in broad 

 level river-margins subject to periodic overflow, where hundreds 

 of square miles become covered with a shallow bed of slowly 

 moving water, or in basin-like depressions, sometimes of vast 

 extent, where from time to time water rises above the level of the 

 horizontal roots. Then these stake-like protuberances, rising in- 

 to and through the current formed by the drainage or by the 

 winds, catch and hold ai-ound the roots of the parent trees many 

 thousand pounds of ' -plant-food' ' in the form of reeds and grass, 

 or small twigs among which dead leaves become entangled. 

 The tree that exclusively possesses this source of nutrition is at an 

 advantage over all others in the neighborhood; and the higher 

 these attenuated ' ' drift-catchers ' ' rise in the stream, the more 

 drift will they an-est, for the highest stratum of water is richest 

 in float. The theory that some disting-uised writers have sug- 

 gested that the knee is a factor in the aeration of the sap and 

 that the tree's death is prevented by such aeration taking place 

 in the upper poition of the knee during periods of high water, 

 would seem to need careful experimental confii-mation. Where 

 Nature forms an organ whose purpose is to preserve the life of 

 the individual, she takes special care to adapt such organ to the 

 function it is depended upon to perform. In this case the rough, 

 dry bark of the knee offers a most imperfect means of access for the 

 oxygen or other gases of the atmosphere to the interior vessels of 

 the plant, and instead of presenting broad surfaces of permeable 

 membrane, formed for ti-ansmitting elastic fluids, at its upper 

 extremity the protuberance becomes more naiTow, and presents 

 less surface as it rises, so that when, during periods of high 

 water, the life of the tree is most jeopardized, the life-saving or- 

 gan attains its minimum capacity. In the presence of this mani- 



fest want of adaptation, it also seems important for the accept- 

 ance of the aerating theory, that some one should experimentally 

 show that the aerating organ of the cypress really aerates 

 to an extent sufficient to make it . of material advantage to the 

 plant. The chemical theory of the cypress knee seems to be but 

 a revival of the elaborate hypothesis of Dickinson and Brown, 

 published in their memoir on T. distichum in the American 

 Journal of Science and Arts, in January, 1848. These industri- 

 ous observers discard the mechanical theory entirely, and con- 

 sider both the spongy knees, and, strangely enough, even the 

 spreading base of the tree, as organs of communication with the 

 air, forgetful that the successful and most celebrated lighthouse 

 in the world^ — the Eddystone — was avowedly modelled after a 

 similar sjDreading tree-base for the purpose of withstanding the 

 storm shocks of the English Channel. By means of a curious 

 drawing they show how the swollen portions of the base rise ' ' to 

 the top of the highest water level, which must, in some instances, 

 attain an elevation of at least twenty-five feet ; ' ' thus continuing 

 the functions and the stiaicture of the knees, ' ' up the body of the 

 ti-ee to the atmosphere. ' ' 



It was long ago observed that no knees are developed when the 

 tree gTows in upland upon a firm bottom, in which ordinary sim- 

 ple roots can obtain in the ordinary way the hold necessary to 

 resist overturning forces, and where there is no stratum of water 

 to transport food. So conservative is Nature, that she reverts to 

 an original or adopts a simpler form of root even in a single 

 generation, if the need for the more complicated aiTangement 

 ceases to exist. 



Finally, I may perhaps be permitted to add an observation re- 

 garding the roots of other trees that trench upon the same soils 

 affected by the cypress, and often take advantage of the anchors 

 it sets so boldly in ti'eacherous bottoms. These trees project their 

 cable-like, flexible roots in every direction horizontally, inter- 

 lacing continually until a fabric is woven on the surface of the 

 soft earth like the tangled web of a gigantic basket. Out of this 

 close wicker-work, firmly attached to it, and dependent for their 

 support upon its integi-ity, rise the tree-trunks. Thus slowly, 

 and by a community of growth and action, a structure is formed 

 that supplies for each tree a means of resisting the storms. 

 Such communities of trees, provided with ordinary roots, advance 

 against and overcome enemies where singly they would perish in 

 the conflict. The cyclone, the loose sand, the morass, — these 

 are the enemies they contend with, as it were, in unbroken pha- 

 lanx, shoulder to shoulder, their shields locked, their spears 

 bristling against the foe ; but the graceful plumed cypress, the 

 knight-errant ■ of the sylvan host, bearing with him his trusty 

 anchor, — the emblem of hope, — goes forth alone and defiant, 

 afar from his fellows, scorning the methods of his vassals, and 

 planting himself boldly amid a waste of waters, where no other 

 tree dare venture, stands, age after age, erect, isolated, but ever 

 ready to do battle with the elements. TV'enty centuries of di-iv- 

 ing rain and snow and fierce hurricane beat ujion his towering , 

 form, and yet he stands the there, stem, gray, and solitary sentinel 

 of the morass, clinging to the quaking earth with the grasp of 

 Hercules, to whom men were building temples when his warden- 

 ship began. 



Robert H. Lajiboen. 



THE GESNER RUST-PROOF PROCESS. 



In Science of Dec. 27, 1889, we printed a report by Professor 

 Haupt on the hydi-ogen process of protecting iron against coito- 

 sion. Since that report was made, a long and exliaustive series 

 of experiments have been carried out by Dr. G. W. Gesner of this 

 city, with the result of greatly improving the process, making 

 it more uniform in its effects, simpler in operation, and less ex- 

 pensive in cost. The general features of the process are the same 

 as described in Professor Haupt' s reports, but the operations have 

 been so simplified that the process may now be worked on a 

 commercial scale by any workingman or laborer of ordinary in- 

 telligence, after a little practice and insti'uction. 



Dr. Gesner has now in constant operation in Brooklyn a plant 



