210 



THE FLOWER. 



respects their structure, and in the Glossary as respects ter- 

 minology. 



384. But into some bristles, such as those of Drosera, a sub- 

 jacent stratum of tissue enters, including one or more ducts or 

 even some woody tissue. Prickles are of this class ; and from 

 the most slender, which pass into bristles, there are all grada- 

 tions of stoutness and induration. Such outgrowths may even be 

 formed in most regular order, as the prickles on the calyx-tube 

 of Agrimonia and scales on the acorn-cup of Oaks, and yet have 

 no morphological importance. On the other hand, true represen- 

 tatives of leaf or stem may, by abortion and depauperation, be 

 reduced to the structure as well as the appearance of trichomes. 

 Examples of this are familiar in the pappus (answering to limb 

 of the calyx) of many Composite, and in the bristles which 

 answer to perianth in many Cyperacese. The scarious stipules 

 of Paronychia and of Potamogeton, the ligule of Grasses, and 

 even the corolla in Plantago, are equally reduced to mere cellular 

 tissue. So that the structural difference between trichomes and 

 outgrowths 1 is not at all absolute, and the morphological distinc- 

 tion must rest upon other ground than anatomical structure. 



385. Among the corolline outgrowths most akin to chorisis is 

 the Crown ( Corona) of Silene and allied Caryophyllaceae, at the 



junction of the claw 

 with the blade of 

 the petals (Fig. 403), 

 the analogy and 

 probable homology 

 of which to the ligule 

 of Grasses (Fig. 

 150) is evident ; also 

 the many-rayed fila- 

 mentous crown of 

 Passion-flowers (Fig. 404) , which consists of two or more series 

 of such outgrowths. In Sapindus and some other Sapindaceae, 

 these ligular outgrowths or internal appendages are more like 

 a doubling of the petal ; as also in Erythroxylum, where they 



1 This is the best English name for the Emergenzen of the Germans, the 

 Epiblastema of Warming, &c. For the development and discussion of this 

 subject, see Warming, in Kjobenhavn Vidensk. Meddel. 1872, and a larger 

 treatise on Ramification in Phanerogams, Copenhagen, 1872. Also, Uhl- 

 worm in Bot. Zeit. 1873 ; Celakowsky in Flora, 1874 ; and Eichler's note on 

 Emergenzen in Bliithendiagramme, i. 48. 



FTG. 403. Petal of Silene Pennsylvanica, with its crown. 

 FIG. 404. Flower of Passiflora caerulea, reduced in size. 



