114 MORPHOLOGY, OR COMPAKATIVE ANATOMY. 



(fig 1 . 203) ; and it runs into the labiate form by such corollas as those of 

 Melampyrum c., becoming tubular in Digitalis. Forms allied to this 

 occur commonly in Bignoniaceaa, Gesneraceae, Acanthaeere, c. 



When the throat of a bilabiate or irregularly lobed tubular corolla is 

 widely opened, it is called ringent or gaping. 



Outgrowths from Petals. Petals when distinct sometimes ex- 

 hibit appendages on the inner face which have been interpreted as 

 stipulary, as in Lychnis (fig. 204) ; in Ranunculus we find a minute 

 scale at the base, and in Parnassia a largish scale, simple or divided, 

 and of glandular character. In gamopetalous corollas we often 

 find a circle of scales in the throat, either free or confluent into 

 \vhat is called a coronet (corona), sometimes developed so far as to 

 produce a long tube projecting from the throat. In other cases 

 there is simply a ring of hairs in the throat (Mentha, &c.). In most 

 cases the scales are in front of the lobes of the corolla (fig. 205), 

 rarely alternate and opposite to the sinuses. 



Examples of circles of scales in the throat occur especially in the 

 Boraginacese (Myosotis, Symphytum, c.), in Cuscuta, &c. In Narcissus 

 poeticus and other species the corona is a complete ring, while in JV. 

 pseudo-narcissus (the Daffodil) it forms the deep yellow tube projecting 

 from the centre. Some authors attribute these structures to chorisis, 

 others rearard them as representing a circle of regular stamens in an abor- 

 tive condition ; and the alternate scales of Samolus may represent an 

 abortive circle of stamens, as this would restore the symmetry of the 

 flower. Usually, however, they are mere outgrowths from the petals, 

 formed by enation at a late stage of development. 



These structures, by a confusion of terms, have been called nectaries and 

 nectariferous scales. The terms scale and coronet are more 

 exact and convenient. Fig. 206. 



Duration. The corolla is caducous, deciduous, or /7I| 



persistent, like the calyx. Occasionally it falls away it 



in part by a circular slit, as in Orobanche and Rldnan- ^M 

 thus. 



In Vitis the caducous corolla separates from the recep- ^Se v1ne We The 

 tacle at the bases of the petals, which cohere above and petals, cohering 

 fall off like a little star when the flower opens (fig. 206). l Srtn *2 

 The corolla is mostly deciduous j it is persistent in Cam- star - shaped 

 panula. P iece - 



In withering, the petals are sometimes closed (occlusa'], as in Eclieveria, 

 spreading as in Boussingaultin, reflexed as in Begonia, crisped as in Pavia, 

 pulpy as in Tradescantia, circinate as in Capparis, recircinate as in Mesem- 

 bryanthemum, and conduplicate as in some species of Ornithogalum. 



The Perianth, in a special sense (see p. 104), consists of the 

 floral envelopes when composed of two circles of similar organs, 

 so that, except in position, there is no difference to be seenbetw r een 



