82 



PRINCIPLES OF PLANT-TERATOLOGY. 



club-moss (Ly cop odium), Selaginella, etc., in which the 

 main body of the shoot divides into two equal or 

 unequal parts ; it is distinguished from axillary branch- 

 ing, which is the normal type for Phanerogams, by the 

 fact that in the latter the main axis does not divide at 

 all, and subsidiary shoots arise laterally in the axils of 

 the leaves. 



This is the only criterion of difference between the 

 two types of branching which is here recognized. 

 A study of fasciated shoots has led independently to 

 the same conclusions as those of Velenovsky and 

 Schoute,* viz., that a contemplation of the mature 

 structure is ample for distinguishing between dicho- 

 tomy and monopodial branching, and that, as Schoute 

 has pointed out in detail, a reliance on developmental 

 data for the determination of what is, or is not, true 

 dichotomous branching, as, e. g. 3 whether there is 

 division of the apical cell or not (the artificial criterion 

 of the orthodox text-book), is entirely misleading. 



A dichotomizing or bifurcating stem and a fasciated 

 stem represent essentially one and the same pheno- 

 menon. Many cases of each are known in Angio- 

 s perms. A bifurcated shoot is merely one which has 

 reached the first stage in the direction of fasciation. 

 Its axis divides into two, not necessarily equal parts 

 only ; while in the fasciated shoot the axis may divide 

 into several parts at the apex, which is the commonest 

 case ; or the ribbon- stem may undergo no apical 

 splitting whatever. t 



Abnormal dichotomy (simple forking) has been 

 observed in the stem of the Jerusalem artichoke 

 {Helianthus tuberosus), in Msesa ramentacea (fig. 22), 

 the wall-flower (Cheiranthus Cheiri), and the stone-hore 



# See his splendid treatise on the branching of Hyphsene. 



f The ordinary text-book definition of "dichotomy" cannot be accepted, 

 viz., a division involving the bisection of the apical cell into two equal 

 halves ; this should be regarded as merely a special instance of the pheno- 

 menon ; it would not cover the cases of stem-forking in Lycopodium and the 

 Phanerogams, which possess no apical cell. " Dichotomy" should be denned 

 as a division of the organ, from the apex downwards, into two parts of 

 equal rank, although not necessarily of equal size or development. 



