126 COMPOUND ORGANS OP PLANTS. 



most part of a greenish hue, chlorophyl being formed in their 

 cells, and stomata or pores existing on their lower epidermis ; 

 and in some cases of monstrosity, they are actually converted 

 into the ordinary leaves of the plant. In proliferous states of 

 the rose, the calyx assumes a leafy aspect ; whilst in Gentiana 

 campestris and Gentiana crinita, it differs in no respect from 

 the ordinary leaves of the plant. 



The sepals of the calyx are sometimes separate from each 

 other as in the buttercup, at other times they are united to a 

 greater or less extent, as in the Polyanthus. When the sepals 

 are separate from each other, whatever may be their number the 

 calyx is polysepalous (jtofos many, sepala leaves;) but the term, 

 as currently understood amongst botanists, is simply used to 

 express the absence of cohesion amongst them, and is equiva- 

 lent in meaning, to the expression sepals distinct. When the 

 sepals of the calyx are united to each other by their margins 

 in a greater or less degree, the calyx is monosepalous (^01/05 

 one, sepala leaf.) The same remarks apply to the petals of the 

 corolla, which are polypetalous or monopetalous, according as 

 the petals are separate from each or in a state of cohesion. 



It is well known that the parts of plants which grow closely 

 together are apt to cohere, the parts anastomosing with each 

 other. Accidental unions of this kind among the leaves of 

 plants are of frequent occurrence. Now owing to the non- 

 development of the floral internodes, the metamorphosed leaves 

 which constitute the flower are necessarily brought into closer 

 contact, and hence they are more frequently found united with 

 each other than the leaves of the stem. 



The sepals of a monosepalous calyx may cohere together 

 by their bases, or by their margins, through their inferior half, 

 or through their entire length, and various terms are employed 

 to express these different degrees of cohesion. 



