191 

 Discoid Pith in AVuody Plants. 



By F. W. Foxwortiiv. 



The occurrence of a discoid pith. i. e., one which is interrupted at 

 frequent intervals by cross partitious variously knoTV'n as disks, dia- 

 phragms, plates or lamellre, has been noted by numerous observers 

 in certain of the woody plants. 



The first mention of it seems to have been by the Anatomist GreAV 

 <Anat. Plantarum. 1082. PI. 19, f. 4i, who described and figured it in 

 Jiiijlans. 



Ch. Morren. in the Ann. Xat. Hist., Vol. 4, No. 22, 1839, gave a good 

 historical sketch of the oliserved cases of discoid pith, and described in 

 detail and figured certain forms. 



W. C. Williamson (Proc. Man. Fit. and Phil. Soc. for 1851) in a paper 

 "On the Structure and affinities of the plants hitherto known as Stern- 

 bergise"— described the casts of this kind of pith which had been con- 

 sidered entire fossil plants— with the group name Stenibergke, and 

 showed their true nature and affinities— as members of the genus Dad- 

 oxyJon Brongn. He also mentioned the occurrence of discoid pith in a 

 number of recent plants. 



M. Gris, in his verj' painstaking work "Sur lamoelle les plantes 

 ligneuses" (Ann. des Sci. Nat. ser. 5. No. 14, 1872), described two struc- 

 turally distinct forms of discoid pith. The first, which he terms Hetero- 

 genous Continuous Diai)hra<jinatic. has the pith continuous between the 

 disks, e. g. Liriodendron. 



The second he terms Heterogenous Diseontinnoiis Diaiihntiiinut'n- and, m 

 this, the pith is not continuous between the disks, the interspaces being 

 empty or filled with air, e. g. Jiif/lans. 



Pith of the first type occurs in Liriodendron and Maf/nolia speeies. in 

 Asiniina and some other representatives of the Anonacew, in Nijssa. and, 

 according to Solereder (Anntomie der Dicotyledonen, Stuttgart, 1899), in 

 many of the Ternxtrm inincew. as well as in Bntchiinema {Ehenaeeev) and in 

 certain of the Cojirolnihiccee. 



