26 COROLLA. 



The calca or spur is a tubular elongation of the re- 

 gular petal itself ; the above are superadded abortions 

 of other petals or of stamens. 



151. In monochlamydeous flowers, or those having one 

 floral envelope only, it is not always easy to determine 

 whether it is a calyx or a corolla. Though the calyx is 

 generally of a green colour, of leaf-like appearance and 

 texture, continuous with its stalk or peduncle, and its 

 divisions opposite stamens, there are exceptions ; and 

 even where both calyx and corolla exist, in some cases 

 we cannot put a limit between the two, the calyx seems 

 to pass into the corolla, and the corolla into the calyx ; 

 and though the corolla is mostly coloured and delicate 

 in texture, and its divisions alternate with the stamens, 

 we have exceptions to these, so that when one envelope 

 only is present, its true nature may be doubtful. In 

 most of such cases we may look upon the co\ r ering as 

 being rather of a corollaceous than a calycaceous nature. 

 The restricting of the term perianth to such a struc- 

 ture, would prevent an application of a wrong term, 

 though it might serve, as Dr. Lindley well remarks, 

 as an evasion of the task of ascertaining its true 

 character. 



152. The spatha is a form of perianth consisting of a 

 large, more or less coloured, foliaceous expansion, which 

 serves as a general floral covering to what is termed a 

 spadix. (See fig. 28, b.) Perhaps, in most cases, this 

 is more truly a bractea. 



153. The already described forms of floral envelopes 

 are foliaceous or petaloid ; there exist others which are 

 termed glumaceous, such are seen in the Grasses. They 

 are considered by many as being more of the nature of 

 bractese than of calyx or corolla, and undoubtedly some 

 portion of what we have to describe is so, but the others 

 appear to me so analogous to the forms of structure 

 we are at present speaking about, that we shall notice 

 them here. 



154. Take a cluster of flowers (a), (which is here 

 called a locusta), say of the common reed, farundoj, and 



