300 REPRODUCTIVE ORGANS. CHAP. III. 



corolla is persistent. An attempt was made to 

 strengthen the rule by adding that the petals of the 

 corolla are thinner and more delicate than the divi- 

 sions of the calyx. But although this is also very 

 generally the case, the fact is occasionally quite the 

 reverse, as is evident from several of the preceding 

 examples, in which the calyx has more the ap- 

 pearance of a corolla than the corolla itself ; as well 

 as from the single envelope of the genus Potygonum 

 and some others, which seems to participate partly 

 of the nature of calyx and partly of the nature of co- 

 rolla; the divisions being green and fleshy throughout 

 the great part of their extent, but thin and finely 

 coloured on the margin. 



By Lin- It had been an opinion of Caesalpinus that the 

 calyx is merely a continuation of the outer bark of 

 the plant or flower-stalk ; and upon this foundation 

 Linnaeus establishes a test apparently sufficient to 

 distinguish the calyx from the corolla in all doubt- 

 ful cases. For, improving upon the notion of 

 Caesalpinus, he apprehended that as the calyx is a 

 continuation of the outer bark of the plant or 

 flower-stalk, so the corolla is a continuation of the 

 inner bark. And hence, if of these two organs one 

 only is present, you have but to ascertain in what 

 part of the bark it originates, in order to say which 

 it is. This summary and decisive test looks indeed 

 very beautiful in theory ; but the observations of the 

 acute and sagacious Hedvvig have shown that it is 

 not founded in fact. 



