66 



SCIENCE. 



[Vol.. XV. No. 365 



dark intervening cloud, which from time to time excludes the 

 rays of the sun. The delicacy of its color and the texture of its 

 leaves exceed everything in vegetation. , . . Prodigious 

 butti'csses branch from the trunk on every side, each of which 

 terminates underground in a very large, strong, serpentine root, 

 which strikes off and branches every way just under the surface 

 of the earth, and from these roots grow woody cones, called 

 Cypress knees, four, five and six feet high, and from six to eigh- 

 teen inches and two feet in diameter at the base." Elliot 

 (Botany of South Carolina and Georgia, 1834, p. 643) says, 

 ' • This cypress resists the violence of our autunmal gales better 

 than any other of our forest -trees."' By my friend. Dr. J. S. 

 Newberry, whose extended geological labors have led him to 

 examine many widely separated cypress-bearing regions in the 

 Mississippi valley and elsewhere. I am assured that he remembers 

 no instance of the overthrow by the wind of a living T. distichum. 

 The surprising and characteristic temerity of the tree is accom- 

 panied by another striking peculiarity : it almost invariably, in 

 soft soils, tln'ows upward from the upper surface of its roots con- 

 spicuous protuberances that are known as ' • cypress knees. ' ' 

 Professor Wilson, who has made a careful and valuable study of 

 the species in the forests of southern Florida, and also by culti- 

 vation, writes, regarding the formation of these protuberances, 

 ' ' Tire small roots, which are six or eight inches below the sur- 



HYPOTHETICAL 



face, grow upward, . . . and, vipon reaching the surface, 

 turn and go down into the soil ; " . . . ' • at each point 

 where the root comes to the surface, begins later the development, 

 on its ujjper side, of the so-called ' knees. ' " In the organ of 

 the Pennsylvania Forest Association Forest Leaves (December, 

 1889), is an excellent article by Professor Wilson on the T. dis- 

 tichum, and a remarkably fine engTaving of a tree with enormous 

 knees. 



These seemingly abnormal growths have attracted much atten- 

 tion, and for more than half a century have furnished an enigma 

 to the solution of which scientific travellers have addressed them- 

 selves. Michaux made a careful study of the cypresses, and in 

 his '-Sylva, " jjublished in 1819, says, "The roots are charged 

 with protuberances eighteen to twenty-four inches high. [I have 

 ridden among them in central Florida in temporarily dry upland 

 basins, where they arose to my breast as I sat upon the saddle, 

 and were not less than seven feet in height above the root.] 

 These protuberances are always hollow, and snrooth on the sur- 

 face, and ai-e covered with a reddish bark, like the roots, which 

 they resemble in softness of wood. They exhibit no sign of veg- 

 etation, and I have never succeeded in obtaining shoots by 

 wounding the surface and covering it with earth. They are 

 peculiar to the cypress, and begin to appear when it is twenty to 

 twenty-five feet high. ' ' Michaux adds, with the frankness nat- 

 ural to a scientific mind, ' ' No cause can be assigned for their 

 existence." Hoopes says, in his " Book of Evergreens " (1868), 

 • ' No apparent function for which the knees are adapted has been 

 ascertained." And Veitch,_ who seems to have studied the pro- 

 tuberances in England, gives in his " Manual" (1881, p. 216) a 



picture of a tree growing at Ilesworth, surrounded by scores of 

 knees, and says, ' ' They are peculiar to this cypress, and no 

 cause has been assigned for their existence. " ' That the question 

 continued in this unilluminated condition until recently, was 

 shown in 1882, when I had the privilege of visiting, in com- 

 pany with the highest botanical authorities, Dr. Gray, Thomas 

 Meehan, John H. Eedfield, Jolm Ball, Professor Carruthers, and 

 others, the classic collection of ti-ees planted by William Bartram 

 on the borders of the Schuylkill. There we examined a fine 

 cypress and the knees it had produced. Dr. Gray then told me 

 that the use to the ti-ee of the knees was unknown I remarked 

 that they might be a means of raising a point on the root above 

 surrounding water, to the end that a leaf-bearing shoot could 

 readily sprout therefrom. To this suggestion he made the same 

 statement made by Michaux and above recorded. Unaware that 

 the subject had been so thoroughly investigated, I have since that 

 period examined hundreds of living ' ' knees ' ' in southern 

 swamps, and found upon them no trace of bud, leaf, or sprout, 

 except where some seed may have lodged in a decayed or de- 

 pressed portion of the surface, and there taken rooc. 



In 1887 I had the good fortune to find a numbei; of cypress- 

 trees under such unusual conditions that their aforetime subter- 

 ranean anatomy could be studied without obstruction ; and I 

 reached a conclusion respecting the use to the ti'ee of the protu- 

 berances, which I have retained in my note-book, awaiting an op- 

 portunity to make sojne further illustrative sketches before 

 placing it before botanists. Some recent publications on the sub- 

 ject, by widely and favorably known authors, have, however, 

 ascribed to the cypress-knees the sole function of aerating the sap 

 of the parent tree, and this idea bids fair to become embedded in 

 botanical literature. Therefore this commimication comes to 

 you earlier than I had purposed sending it. 



Stretches of the shore of Lake Mom-oe, in central Florida, are 

 closely set with large cypress-trees. They grow in various kinds 

 of bottom, — clay, mud, and sand. Those of which I shall here 

 speak stood in sand so loose that, when the level of the water 

 was lowered, the waves readily washed it awa.y, and cai'ried it 

 into the depths of the lake. Some four vertical feet of the root- 

 system was thus finely exposed. After several days spent in ex- 

 amining a score or more large trees that had been thus denuded, 

 I became convinced that the most important function of the 

 cypress knee is to stiffen and sti-engthen the root, in order that a 

 gi-eat tree may anchor itself safely in a yieldins' material. 



The word ' ' anchor ' ' is indeed an apt one here ; for the living 

 root, curved to its work, and firmly grasping the sandy bottom, 

 suggests vividly the best bower-anchor that a man-of-war may 

 throw- into similar loose sands, when tlu-eatened by the very at- 

 mospheric forces that the Taxodium has been fitting itself to 

 resist since tertiary times. Professor Shaler, in a most interest- 

 ing treatise on the nature and associations of T. distichum, shows 

 that the cypress which existed in the miocene age has since then 

 probably gradually changed its habitat from the drier ground to 

 to the swamp areas. 



Truly a most admirable and economical aiTangement to stiffen 

 and sti'eBgthen the connection between the shank of the anchor 

 and its fluke is this knee ; and usually in the living anchor the 

 fluke branches or broadens as it descends, so that its effectiveness 

 is greatly increased, like the sailor's anchor of many flukes, or 

 the ' 'muslu'oom anchor' ' that he may have learned to depend 

 upon where the bottom is softest. 



The accompanying picture is from a photograph that I made in 

 1887 of the lower portion of a ti'ee that rises some seventy feet 

 above the shore line of Lake Mom-oe. The original surface of the 

 sand was near the level of the higher roots. The picture shows 

 the manner in which this peculiar species tlu-ows out horizontal 

 roots from its conical (usually hollow) butti-essed base. At 

 different distances from this conical base these horizontal roots 

 project strong branches more or less perpendicularly into the 

 earth. "Wliere such perpendicular "flukes" branch from the 

 main horizontal "shank," it will be seen, there is formed a 

 large knob, which is the ' -knee" ' under discussion This knee, 

 when fully developed, is generally hollow, comparatively soft, 

 gnarled, and very difficult to rupture, so that it has the quality 



