196 



Fig. 156. 



Pelorium of Digitalis 

 pur pur ea monstrosa. 



rium of perfect ternary symmetry. x ) This remarkable phenomenon 

 is commonly observed in the flower which stands at the apex of a 



stem or in the centre of an inflorescence, 

 and the changed flower has moreover a 

 tendency to take a more upright direction 

 of growth than is usual for it. (Antirrhi- 

 num maius', Digitalis; etc.). When such 

 an irregular blossom becomes symmetri- 

 cal, this may occur in two different ways : 

 either the development of such parts 

 which determine the lack of symmetry in 

 the ordinary individuals, is stopped, or the 

 irregular parts are produced in greater 

 number, so that a higher symmetrical com- 

 plex is the final result. In the first case it is 

 said that a "regular pelorium" is produced, 

 in the latter case the "irregular" one. 



The regular pelorium is therefore a 

 product of stagnation in the natural 



development of the blossom, the irregular pelorium is the result 

 of an excessive development of certain parts of it. 



At present the phenomenon is generally explained in both cases 

 as a retrogression towards an older prototype. According to this 

 view, the occurrence of peloria is a case of atavism, of typical re- 

 trograde mutation. The irregular or less symmetrical flower is the 

 descendant of a higher symmetrical ancestor; and also here the older 

 form therefore appears to be that of higher symmetry. 



Indeed, it can hardly be denied that there is a sharp line of 

 demarcation between the forms of inanimate and living nature 

 with respect to the part the principle of symmetry takes therein: 

 here the gradual evolution of forms from higher towards lower sym- 

 metry, and the characteristic preference for the irrational ratio of 

 the "aurea. sectio"; there the tendency towards higher symmetry 

 as to a condition of greater mechanical stability, and the exclusion 

 of all irrational ratios in the periods of the symmetry-axes. There 

 is no way to escape the urgency of this conclusion, and only the 

 question may arise : can we hope that further investigation shall 

 enable us in future to overcome this barrier? 



1) M. T. Martens, Nat. Hist. Review, (1863); Vegetable Teratology, (1869). 



