XI 



THE CYMOSE INFLORESCENCE 



767 



of parts successively and permanently laid down. The shell-less 

 molluscs are never spiral; the snail is spiral but not the slug*. In 

 short, it is the shell which curves the sr^ail, and not the snail which 

 curves the shell. The logarithmic spiral is characteristic, not of the 

 hving tissues, but of the dead. And for the same reason if will 

 always or nearly always be accompanied, and adorned, by a pattern 

 formed of "hues of growth," the lasting record of successive stages 

 of form and magnitude!. 



The cymose inflorescences of the botanists are analogous in a 

 curious and instructive way to the equiangular spiral. 



In Fig. 365 B (which represents the Cicinnus of Schimper, or cyme unipare 

 scorpioide of Bravais, as seen in the Borage), we begin with a primary shoot 

 from which is given off, at a certain definite angle, 

 a secondary shoot: and from that in turn, on the 

 same side and at the same angle, another shoot, and 

 so on. The deflection, or curvature, is continuous 

 and progressive, for it is caused by no external 

 force but only by causes intrinsic in the system. 

 And the whole system is symmetrical: the angles 

 at which the successive shoots are given off being 

 all equal, and the lengths of the shoots diminishing 

 in constant ratio. The result is that the successive 

 shoots, or successive increments of growth, are 

 tangents to a curve, and this curve is a true 

 logarithmic spiral. Or in other words, we may 

 regard each successive shoot as forming, or defining, 

 a gnomon to the preceding structure. While in 

 this simple case the successive shoots are depicted 

 as lying in a plane, it may also happen that, in addition to their successive 

 angular divergence from one another wildiin that plane, they also tend to 



Fig. 365. A, a helicoid; 

 B, jbl scorpioid cyme. 



* Note also that Chiton, where the pieces of the shell are disconnected, shews 

 no sign of spirality. 



t That the invert to an equiangular spiral is identical with the original curve 

 does not concern us in our study of organic form, but it is one of the most beautiful 

 and most singular properties of the curve. It was this which led James Bernoulli, 

 in imitation of Archimedfes, to have the logarithmic spiral inscribed upon his tomb; 

 and on John Goodsir's grave near Edinburgh the same symbol is reinscribed. 

 Bernoulli's account of the matter is interesting and remarkable: "Cum autem 

 ob proprietatem tam singularem tamque admirabilem mire mihi placeat spira 

 haec mirabilis, sic ut ejus contemplatione satiari vix nequeam: cogitavi iUam 

 ad varias res symbolice repraesentandas non inconcinne adhiberi posse. Quoniam 

 enim semper sibi et eandera spiram gignit, utcunque volvatur. evjlvatur, radiet, 

 hinc poterit esse vei sobolis parentibus per omnia similis Emblema: Simillima 

 Filia Matri; vel (si rem aeternae veritatis Fidel mysteriis accommodare non eat 



