258 



ORGANOGRAPHY. 



2. THE DISK. 



The application of the term disk is variously understood by 

 botanists : thus, by some it is used as synonymous with thalamus, 

 receptacle, or torus ; by others it is understood to include all 

 abnormal or irregular bodies of whatever form, which are situated 

 on the thalamus between the androecium and gyncecium ; by 

 others, again, it is defined as that part of the thalamus which 

 is situated between the calyx and the gyncecium, and which 

 forms a support to the corolla and androscium ; while otliers, 

 again, define the disk as the portion of the thalamus situated 

 between the calyx and gyncecium, when that part assumes an 

 enlarged or irregular appearance ; while by others, again, the 

 term disk is understood to include all bodies of whatever form 

 which are situated on the thalamus between the calyx and gynce- 

 cium, or upon or in connection with either of these organs, but 

 which cannot be properly referred to them. It is applied in 

 the latter sense in this volume. 



Although the disk is not an essential organ of the flower, it is 

 best treated of in this place, as it is most commonly placed be- 

 tween the androecium and gyncecium, and therefore comes next in 

 order to the androecium as we proceed with our examination of the 

 parts of the flower. The disk seems, in many cases at least, to be 

 merely a modification of the stamens, which appears to be proved, 

 not only from its parts occasionally alternating with them, as 

 in Gesncra, but also from the circumstance of portions of it 

 when highly developed becoming occasionally changed into sta- 

 mens. It is fr^qtieiitly of a nectariferous nature, and hence was 

 treated of by Linnaeus and many succeeding botanists under the 

 name of neclaries. 



Fig. 563. 



Fig. 564. 



i^'ic?. 5G3. Flower of i\\eV^v,rn;\ {Fmniculmn"\. Theovary is surmonnted by 



a disk, d. F/r/. 5G4. Flower of tlie Kue (J?Mtffl (77Yti-eo/ens). Tlie pistil 



is surrounded liy a disk in th(3 form of a flesliy riiig, on the ontside of 

 wbicli the stamejis arc inserted. 



The disk is developed in a variety of forms; thus, in the 

 Orange and Hue {fig. 564) it forms a fleshy ring surrounding 

 the base of the pistil ; in the Tree Pseony {fig. 565) it occurs 



