96 THE PLANT ' WORLD. 



" It was found, in confirmation and extension of the less com- 

 plete observations of Prantl and Simon, that the roots of ferns 

 never truly regenerate themselves as do those of flowerino- plants. 

 Possibly the diiTerence is to be attributed to the more definite con- 

 centration of formative protoplasm in the apical cell of the former 

 as contrasted with its "reater extension as layers in the roots of 

 the latter. At any rate, no regeneration occurs in the roots of 

 ferns, although some attempts at healing the actual wound may 

 be made. 



" The case is diiTerent with the roots of phanerogams, although 

 in them, also, the conditions of regeneration are more limited 

 than might have been anticipated. In the first place, no union 

 of the halves of longitudinally cut roots took place ; the damaged 

 apex was either replaced b}- a new one on either side of the slit or 

 else the regeneration was confined to one half. 



" Lateral incisions are inefifective to bring about the difl:'erent- 

 iation of a new apex unless the slit has severed at least half the 

 circumference of the pericycle. If this be done, regeneration 

 takes place with the concomitant appearance of statolith starch in 

 the new organ. All the experiments made on the roots go to 

 emphasize the great importance of the pericycle in connection with 

 regenerative processes, although it is not from this layer itself that 

 the new layer is differentiated, but from the indifferent plerome 

 cells within it. The damage done to the pericycle appears to act 

 as an interruption of the coordinative relations between the vari- 

 ous parts of the embryonic region as a whole. When this co- 

 ordination is interrupted the capacity resident in the embryonic 

 protoplasm of giving rise to entire organs, asserts itself, and the 

 new formation thus appears." 



Labelling Paraffin Blocks.^ — The following may be nothing 

 new, nevertheless it is an excellent way to keep a record of the 

 material embedded in paraffin blocks. On a small paper slip 

 write the name and character of preparation, whether stained or 

 injected, and lay this in the surface of the still liquid paraffin with 

 its embedded material and let it solidify with the block. Or melt 

 the slip on with a hot wire after the block has been cooled. In 



