Prof. LiNDLEY on the Anatomy of the Roots of Ophiydese. 425 



cettes are produced by the pressure upon them of the cells of parenchyma 

 among which they lie. They are tough like horn, cannot be torn, crackle 

 between the teeth like fragments of caoutchouc, and may be easily cut or 

 even sliced, when they seem to be perfectly homogeneous, exhibiting no trace 

 of layers or successive deposits, either when fresh, or after being dried, or 

 when acted upon by ordinary chemical reagents. These nodules are mostly 

 of about the same size, but here and there some are to be seen not larger 

 than the ordinary cells of parenchyma. The latter is thin-sided, in no degree 

 pitted, and is readily coloured brown by the alcoholic solution of iodine or 

 by exposure to air. Each cell bears with considerable regularity a cytoblast 

 upon some part of its walls, and in most of the larger cells there is a small 

 quantity of starch, readily coloured blue by the aqueous solution of iodine. 

 Otherwise the parenchyma contains no solid matter, with the exception of 

 occasional parcels of acicular raphides. 



The nodules are scarcely soluble in cold water, but when boiled they be- 

 come tumid and partially dissolve into a transparent jelly, with a vitreous 

 lustre. If exposed to the air they rapidly dry and become deep brown. The 

 aqueous solution of iodine produces no sensible effect upon them in their na- 

 tural state ; but if they are first treated with caustic potash, or nitric or sul- 

 phuric acids, all which dissolve their contents, they then acquire a deep claret 

 colour when acted upon by alcoholic solution of iodine. 



But although iodine, in the form of the aqueous solution, while it colours 

 blue the grains of starch, produces no sensible effect upon the nodules them- 

 selves, yet it does produce an effect if Ijbe alcoholic solution is employed. 

 In that case the nodules slowly become amethystine, altering to claret colour ; 

 and if the nodules are wounded, the latter colour gradually, but slowly, ex- 

 tends over the wound. These colours, however, soon disappear, especially if 

 the air is warm ; not a trace of blue is at any time observable. The nodules 

 are therefore not starch. Indeed I believe there is no known instance in 

 which this common substance possesses even the organic characters which 

 have been just described ; nor am I aware of any other case of the solid 

 secretions of plants assuming such an appearance as is found in the subject 

 of these remarks. The cysts containing oily matter in the rind of the Orange 

 are, in some respects, most analogous. 



3 K 2 



