APPENDIX. 59 



in each case the point of insertion of the borders of a 

 leaf is approximated to within about three lines of the 

 point of insertion of the central portion of the leaf next 

 above it. If, now, we imagine the lowest internode to 

 expand so much in breadth (without enlargement of the 

 cicatrix), that the meeting borders of the cicatrix would 

 be separated about \ of the breadth of the cicatrix, a 

 portion of stem, nearly eight lines in breadth, must be 

 inserted between the separating borders of the leaf; and 

 during the period of the completion of the structure of 

 this piece of stem, new tissue must be formed in the in- 

 terior; the firm, fibrous layer, already 2*5 lines thick, 

 must enlarge a fifth part of its circumference ; and the 

 inner soft substances must increase in quantity, in like 

 proportion, to fill up the space within this expanded 

 layer. Of all this, no trace can be found in the examina- 

 tion of a stem of Aletris. Instead of what this theory 

 requires, the insertion of an entire segment of a circle 

 between the old parts, and the enlargement of the in- 

 ternal soft substance, we find that the latter, when once 

 formed, remains for ever unchanged, and in like manner 

 no new development is met with, in any part of the sub- 

 stance, of firm woody layers ; but we do find that new 

 fibres and cells are produced uniformly in a true cam- 

 bium layer around it, and upon its outside. This sta- 

 tionary condition of the internal parts of the stem, is 

 again, fully sufficient of itself to refute the whole of 

 Meneghini's theory. But if, disregarding this fact, we 

 imagine the lowest internode, the cicatrix of which in the 

 stem under consideration was 39 lines in circumference, 

 to undergo the change described, this would obtain, 

 by the addition of \ of the size of the base of the leaf, 

 a circumference of 47 lines. In this expansion the 

 next internode above must share^ since we always find 

 the stem of Aletris to be nearly cylindrical. But the 

 part of the leaf next above, which lies only a couple of 

 lines to one side, is situated only about three lines above 

 the borders of the lowest leaf, from which we set out. 



