178 



Morphology of members. 



Just as the dichotomy may consist of numerous bifurcations, so may a mono- 

 podium consist of several orders of monopodial branching. 



These definitions refer only to the bud-condition of the branch -system. Not 

 unfrequently, both in dichotomous and in monopodial systems, the original character 

 is maintained in their further growth; the two bifurcations develope, in the case 

 of dichotomy, with equal strength and branch uniformly ; in the case of a mono- 

 podium the primary axis continues to grow more strongly than all the secondary 

 axes, and branches more copiously. But it is very commonly the case that in 

 a dichotomous system some of the bifurcations are weaker, or that in a mono- 

 podial system some of the lateral axes, soon after their formation, grow more 



strongly and branch more copiously than 

 the primary axis. In such cases the ori- 

 ginal character of the branch-system be- 

 comes less and less evident as it developes; 

 and it may happen that systems originally 

 dichotomous have subsequently the appear- 

 ance of monopodia, and vice versd. It is 

 hence impossible to infer from a mature 

 system whether it originated in dichotomy 

 or in lateral branching. It will therefore 

 be desirable to make a simple classification 

 of the most important changes which a 

 branch-system undergoes during the de- 

 velopment of its members. 



(i) The Developvient of Dichotoinous 

 Systems may take place either in a bifurcate 

 or a sympodial manner; I call a system 

 bifurcate when at each fork the two 

 branches develope with equal strength, as 

 in Fig. 134, A. The dichotomous system is 

 developed sympodially when at each bifurcation one branch developes more strongly 

 than the other ; in this case the base of each successive bifurcation forms apparently 

 a primary shoot, on which the weaker branches appear as lateral shoots (Fig. 134, B, 

 C). The apparent primary shoot, which in fact consists of the bases of consecutive 

 bifurcations, may on this account be termed a Pseud-axis or Sympodium. Thus in B 

 (Fig. 134) the sympodium is composed of the left-hand branches /,/,/; in C of the 

 alternate left and right-hand branches Ir^lr. Whether the case represented in B, 

 which, on account of its similarity to certain monopodial systems, may be termed a 

 Helicoid (bostrychoid) Dkhoiomy, actitally occurs is doubtful (it probably does how- 

 ever in the leaf oi Adiantuin pedaium). On the other hand the development repre- 

 sented in Fig. 134, C is common in shoots of Selaginelleae, and, on account of its 

 resemblance to some monopodial systems, may be termed a Scorpioid (cicinal) 

 Dichotomy \ 



(2) The development of Monopodial Systems may take place in a racemose 



Fig. 134.— Diagram of the various modes of develop- 

 pient of a dichotomy ; A one developed in a bifurcate 

 nianaer ; B » helicoid ; C a scorpioid dichotomy. 



^ On Dichotomous Inflorescences see l^ook II, Phanerogams. 



