191 

 Discoid Titii in AVoody Plants. 



BV F. W. FOXWOETHY. 



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

 frequent intervals by cross partitions variously known as disks, dia- 

 phragms, plates or lamellfe. has been noted by numerous observers 

 in certain of the woody plants. 



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

 <Anat. Plantarnm, 1GS2. PI. 10. f. 4), who described and figured it in 

 JugUins. 



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

 historical sketch of the ol)served cases of discoid pith, and described in 

 detail and figiu'ed certain forms. 



W. C. Williamson (Proc. Man. Lit. and Phil. Soc. for ISolt in a paper 

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

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

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

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

 o.rylon Brougii. He also mentioned the occurrence of discoid pith in a 

 number of recent plants. 



M. Gris, in his very painstaking work '"Sur la moelle les plantes 

 ligneuses" (Ann. des Sci. Nat. ser. 5. No. 14, lS72j, described two struc- 

 turall3^ distinct forms of discoid pith. The first, which he terms Hetero- 

 genous Contiiutoiis Diaphrcigniatie. has the pith continuous between the 

 disks, e. g. Liviodeiitlrnn. 



The second he terms Heterogenous Diseontlnuous Diaphraginnfic and. m 

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

 empty or filled with air. e. g. Jiighins. 



Pith of the first type occurs in Liriodendron and Magnolia si)ceies, in 

 Asimhia and some other representatives of the Anonaeea\ in Niissa. and, 

 according to Solereder (Anatoniie der Dicotyledonen, Stiittgart. 18!i!M, in 

 many of the Ternstroeinidcea'. as well as in Braeliiineina {Khriiarcai and in 

 certain of the Conrolrnlaeeir. 



