DE CANDOLLE'S PHYTOGRAPHY. 301 



But on the same page, to " Corolla sinistrorsum " is ap- 

 pended the foot-note which has made so much trouble, namely, 

 " Sinistrorsum hoc est, quod respicit sinistrum, si ponas Te 

 ipsum in centro constitutum, meridiem adspicere ; Dextrorsum 

 itaque contrarium." That is to say, in defining the direction 

 of overlapping of the parts of a perianth, Linnaeus took the 

 open flower instead of the bud, and proposed to look down 

 upon it from above or within. Now it may well be that Lin- 

 naeus subsequently perceived the contradiction between his 

 terminology for overlapping and that for twining ; and that 

 his brief erratum, on p. 310, " pro sinistrum lege dextram," 

 was intended to bring the former into congruity with the lat- 

 ter, which it does, but in an awkward way. Perhaps he saw 

 the incompatibility of the cited examples ; in fact, about as 

 many of them accord with the outside as with the inside point 

 of view. Any way, the erratum is his own ; it seems unlikely 

 that he authorized its omission from the Vienna editions ; and 

 Gleditsch and Willdenow should not be blamed for heeding 

 his behest in their editions. For, so far as it goes, it tends to 

 render their author consistent with himself. If Linnaeus had 

 revised the page himself, he would have left out the " meri- 

 diem adspicere," which has nothing to do with the matter, 

 and doubtless he would have completed his assimilation of 

 the direction of petal-obliquity or overlapping with that of 

 stem-windins: ; and so the whole confusion from which we 

 are endeavoring to escape would have been avoided. 



In adopting the external point of view — now fortified by 

 original authority — it is well to note that we shall be in 

 accord with the modern physicists and mathematicians, and 

 also with common people. The ordinary screw, on which the 

 thread winds from left to right of the confronting observer, 

 and which is driven home by the semi-rotation of the hand 

 and fore-arm from left to right, is everywhere known as the 

 right-handed screw ; and this, with the corkscrew, is taken as 

 the norm and exponent of right-handed rotation by Clerk- 

 Maxwell (" Treatise on Electricity and Magnetism," i. 23), 

 and by Sir Wm. Thomson. 



The analogies which have been adduced in favor of the 



