S I III BALD i > PR] Sfi •' 



earthquakes of 1811. Whenever this .-inkiiiL' brought the tops of the 



cypress knees below the level of the permanent water, tin' trees all died. 



great areas of Reelfoot and the adjacent lakes are >till covered by the 



stately columns of these trees which were killed in this way two thirds of 



a century ago, and their submerged knees are >till traceable, bo that there 



cannot be any doubt "t' their position; yet other specimens, in which the 



were nearly buried, >till survive. 



In various mill-ponds in this district, when 1 artificial flooding "f the 



swamps ha- brought the permanent level of tin- water above the top of the 



- haves] lily died. 'Phis connection between the tl ling 



of tli.- kill's and the death of the trees to which they belong is well recog- 

 nized by the | pie of th untrv. They ,1., net hesitate to determine the 



• of the summer waters by the altitude of the crests of the knee-. 

 1 n .in- t-i me that these tact-. — viz., the fail me of the knee- to develop 

 when the tne- grow eii high ground; the development of the knees when 

 ire in permanent water: the rise of the knees above the perma- 

 nent water level, and to a height varying with that level; and finally, the 

 destruction of the tree- whenever the level of permanent water rises above 

 the top of tin' knee-, — incontestably show that there is some nccessar] 

 connection between them and the functions of the root- when the latter 

 ermanently submerged 

 It - not unreasonable to conjecture that this function of the knee- i- in 



some u.iv connected with the pr ■-- of aeration of the sap. It is a well 



known tact that the roots of most plant- are intoleranl of continuous im- 

 i :n- likely, therefore, thai some process connected 

 with the exposure of the sap to the air take- place in these protuberances. 

 This 1 ipported by the fact that the knees remain quite vas- 



cular, and that the process of their growth assures the constant exposure 

 sidcrable of newly formed bark on the upper part of the 



circumsta that would favor the aeration of the sap. The « |\ 



part of the knee i, b,uk> verj Bofl and spongy, differing very much from 



linan w 1 of the tree. 



I- - clear that we have in this tn mmodation 



t<> the changeable conditions it ei unters in it- different stations ; ami the 



— with which the variations are brought about must remain a mat 

 who knows the -mall amount of flexibility in this 

 * shown by most 1 do not know of anothi 



