MULTIJUGATE TYPES. 181 



Dipsaceae ; species of Oephalaria affording good illustrations. G. tartarica, 

 Schrad., typically presents terminal capitula of the (10 + 16) type, 

 and all the laterals (8 + 13) (fig. 68a, b) ; the appearance of these 

 is sufficiently obvious in the bud-condition (fig. 69a), and the fact that 

 the bijugate expansion commences normally is shown by fig. 696 ; 

 specially fine terminal heads again show subsequent variations and 

 irregularities. Similarly G. radiata gave (12 + 19) with slight 

 irregularities for the terminal capitulum of a strong plant, (10+16) 

 for aU weaker ones, while all lateral (T', T") were (8 + 13). 



G. leucantha, also terminals (T) (10 + 16), laterals (T', T") (8 + 13), and 

 Scdbiosa atropurpurea, terminals (10 + 16), or (6 + 10) in fruit, and 

 laterals (8 + 13), becoming (5 + 8) in fruit. 



In these plants, however, bijugate construction is only apparent in the 

 terminal capitulum which closes a bijugate (2 + 4) vegetative shoot; 

 this type of asymmetry being lost in the lateral branches in which 

 normal Fibonacci relations are restored beyond the prophyUs. On the 

 other hand, bijugate capitula occur in Dipsacus terminating branches 

 of the first, second, and even third degree as well. The tabulation 

 of the parastichy ratios observed in typical specimens of the commoner 

 species will give the clearest idea of the distribution of multijugate, 

 normal, and anomalous or irregular systems. 



(1.) Dipsacus sylvestris, an average plant, 5 feet high, the terminal capitulum 

 95 mm. by 45 mm. in diameter, over the spines, showed an irregular 

 construction about (30 + 33) at the broadest diameter ;* six other lateral 

 capitula gave in order : — 



30 + 33(irreg.)-J 



(30 + 



T'. 



(27 + 36 (irreg.) 



31 (irreg.) 



/ 26 + 42 

 \ 26 + 42 



/23 + 28 

 \ 24 + 36 



Irregularity thus occurred in the leading capitula, and also in the last-formed 

 basal ones ; two lateral capitula were exactly right, and all would appear 

 to be derivates of the full 16, 26, 42 system. 



(2.) A much finer plant, which had been growing in the open, 6 feet high, 



* Note that in counting irregular systems, the eye is readily misled in 

 following the wavy curves, and an approximation to equality in the ratios is thus 

 often a consequence of confusion of two sets of parastichies. No data for such 

 systems which are not taken from sections can be considered absolutely reliable. 



