358 



EXTERNAL CONFORMATION OF PLANTS. 



(2) An originaUy monopodial hranch-systejn may develope in a racemose or 

 cymose manner ; and the cymose development may be either apparently dicho- 

 tomous (or even apparently polytomous) or sympodial \ 



(a) A racemose system occurs when, with a monopodial origin, the mother- 

 shoot, which is originally stronger, continues also to develope more strongly than 

 all the lateral shoots, and when each lateral shoot of the first order behaves again 

 in the same manner in respect to its lateral shoots of the second order, and so on. 

 This occurs very clearly, for instance, in the stems of most Conifers (especially 

 Pinus, Araucaria, &c.) and in the compound leaves of Umbellifers. 



(b) The cymose development of a monopodial system, or a Cyme, depends 

 on the fact that each lateral shoot, at first weaker, begins from an early period 

 to grow more strongly than the mother-shoot above its point of origin ; and, in 

 consequence of this, also branches more vigorously than the mother-shoot, the 

 growth of which then usually soon ceases. Two principal forms of Cyme may be 

 distinguished, according as a Pseud-axis (Sympodium) is formed or not. 



(a) When two, three, or more lateral shoots arise beneath the growing end of 

 each shoot, which develope in different directions more strongly than their mother- 

 shoot, the growth of which 

 soon ceases, a false Di- 

 chotomy, or Trichotomy, 

 or Polytomy arises. Fig. 

 127 represents the forma- 

 tion of a false dichotomy ; 

 the shoot / produces the 

 shoots //', //'', originally 

 weaker, but soon growing 

 more strongly, while the 

 growth of 1 ceases ; the 

 same takes place with ///' 

 and Iir\ False dichoto- 

 mies of this kind, which 

 occur abundantly in the 

 inflorescences of Phanerogams, are termed by Schimper Dichasia. But instead of 

 two lateral branches growing out in opposite direcdons, three or more shoots 

 standing in a true or spurious whorl may develope more strongly than their 

 mother-shoot, and thus arises an umbrella-shaped or umbellate system, such as is 

 developed in a typical manner in the inflorescences of our native Euphorbias ; 

 a system of this kind may be called a Cymose Umbel. 



(/3) The sympodial development of an originally monopodial system occurs 

 when one lateral shoot always developes with greater vigour than the portion of its 

 mother-shoot which lies above its origin, as is shown, e. g., in Fig. 128, A, where 

 the lateral shoot 2-2 grows more strongly than the part 2-1 of its mother-shoot, 

 and so on. Usually the portions of all the shoots which lie below their lateral 

 branches develope more strongly than the terminal portions, as is shown in the 



^ Here also I deviate from the terminology of the first edition ; not because that was incorrect, 

 but because, by so doing, a greater facility is attained in the mode of expression. 



Fig. 127.— Diagram of a false dichotomy ; the Roman numerals indicate the order of 

 development of the shoots of the system. 



