HAkUWOOU KECOKU 



limiiuiH tliroiiKlxHit, tlioii(;li lln'y ofloii orciir in 8II111II KniiipH or 



M>rl inilinl rows of from two to live veswln. Tli<> vrHncl cavilic* iin- 



lion |>nrtly filloil nitli n iliirk lirovvn oiilwliinfi* ciilloil t.vloiM>)t, uitliiii 



1 hi> >i>s)«>l nivity iix iliirk lir<i»n inniiwH of |iiiri-ncliyinHtniiH tiKHiii- 



I'liilrUn. 



Vessols (Pi){. I) foiiHiHt of iiiiiiioroiiH .iliorl sri'liiciitH (Fi);. I. i.i. ) 



plnrnl «>n<l to emi, niul tlii' pliiiu' of tln> |iiirtitioii wiiIIh ('Fiji. 1, /MC ) 



:it IhiIIi onild of tlio VfHM<l S(>c-iii'iits nrt< iiNiiiilly oli|i<|iii> ami fnro tho 



V III riiys. Till- m-kiikmiIs of ihr l:irj{<T wswls iiro iil)oiit us loiijf 11s 



' '<lv. Tlix vi^KHi-l wiiIIm iiii> iisiinlly t|iiito tliiii, fioldoiii boiiiK ns tliick 



- tlio wnllfj of wood lil«>r!i. I'its (Fig. 1. /»./>.) iiri> iiiinioroim in tlir 



>'-<<w>l walU, ami at |Hiints whorr- vemplK arc in contact with wooil 



I irpni'liynui filn-rs and pitli-rny rolls tlii'y Iwir small Rimpio pilH. and 



Miiftimos narrowly iKirdorfd pits. 



Tlip followint; •"I'''' sliows dianirt.T nii'iisiirrmciils of v.'sscls from 

 •■-.■ wood of different walnuts: 



kItl.K I 



Spcclm 

 Juplann rim nil 

 Juijlaait nigra . . 

 JhuHioh mprMiiK 

 .lufiUini, ftilifonii: 



.MINLMIM ni.V.MKTKIC OK 



si'i;cii:s 



I'riiKi* .Mnxlmnin .Minimum 



'I'rac-beids. wbicli oivur Bparin(;ly in walnut wood arr.-in^i-il aioiiiiil 

 till' vessels (Fig. 1), are ilistinguislied by their thin walls, rather wide 

 Inmiua, blunt ends, bordered pits, and by being shorter than the other- 

 wist- simiewhnt similar wood fibers. 



WOOD FIBGR.S 



Wood fibers are the thiek walled elements which form tiie bulk of 

 the wood. In transverse section they are chiefly round (Plate I, v.f.). 

 but sometimes more or less irregular in outline, particularly those at 

 I lie outer edge of the annual rings and near the larger vessels, where 

 thev are usually much flattened. The cell walls are quite thick, and 

 the <'eil cavities are small, esiiecially in those fibers which form dense 

 tiswue at the outer Ijoundai-y of tlie annual rings. In longitudinal 

 s<>ction wood fibers a]>pear elongated, pointed at both ends, at which 

 they are closely overlapped by fibers above and below (Fig. '2). The 

 hmgth and width of these fibers vary considerably. :is sliowii in the 

 I'ollowing table: 



lARF.K II .VVERAtU:. .M.VXI.MT.M .VNK. MIMMIM I,I:N(;TI !.>< .\.\Il 

 WlfiTIIS OK WALXIT WOOD KIUKUS 



.Vver«K<- Maximum .Mininmm Avcraco 



.S04'. 



.023 



l.li(i:!l 



JU]/IIIHH ttti/ni 1. 



.luiilan* cincrca 1. 



.lufllann ruppalriK 1.047 1.4:!:! 



.lufilanM calitoi-nica l.or.c, 1.417.1 



.\ltbough there is considerable variation in length of filxrs, both 

 of the same species am} also for the four different species, this 

 variation is slight in comparison with that of fibers in wood of the 

 -ame s-]iecies grown under widely different soil conditions. The extent 

 .if this variation is shown in the following table, California walnut 

 \voo<l being taken only as an example of what is true of the other 

 species grown in entirely different .soils. 



lAKI.i; III — MAXI.MIM. MIXIMI .M ANH .VVKUACi: LKXCTIIS" OK 

 KlliKlfS — WOllli OK C.M.IKOUXI.V WAI.M T CKOWX IX 



i)iKKi:iti:xT SOILS 



l.onKthsof Kll)crs in .Mlilimctcrs 

 .Wcrasrc .Maximum .Mlnlmnm 

 ihiirucicr of Siiii mm. mm. mm. 



Ih'op black soil, abundiint 

 growing space 



Moderately moist si 

 and growing spac 



liglit 



l.0i)7 



.428 



bry sand and gravel 008 1.302 ..140 



The pits (Pig. 2, .«.;>.) of wood fibers (best seen in macerated 

 material) are. simple, having slit-like openings about half as long as 

 the width of the cell. These openings, which are often parallel with 



vood 



the axis of the fIberH, are iirrangiMl nitiuilly in a ninKle row ou the 

 radial wallH. 



WIMlli l-.\KKNI 11 V M S KIIIKKH 



WiHid-piireiichymu HbeiH (Fig. 3) are abundiiiit in the Mood of all 



native walnuts. They 1 ur in Ninnll groups, arranged chii'lly in fine, 



irregular tangential lines (Plate III, u.p.f.), or they nniy be iHoInted 

 among thivk-walled wood fibem, and are often in contact with vi-tselh. 

 In transverse Hections they can Ix- readily seen by a hand magnifier, 

 being characterized by thin walls and relatively large cell cavities 

 (Fig. 3, r.r.). The true character of these fibers is best ol:s<>rved. 

 however, in longitudinal sections. Kadi fiber consists of from three 

 to eight rectangular cells placed end to end, the upper and lower cells 

 always ta|H-ring to 11 blunt end (Fig. 3, ii).;».r.). The cross walls 

 (between the inilividiinl cells) are usually horizontal and are always 

 marked by small, round, simple pits (Fig. 3, s.p.). In radial sections 

 the pits are numerous, occurring in small groups or rows, but in 

 tangential sections they appear rather sparingly. Wood-purcneliyina 

 fibers bordering vessels are usually much flattened and have numerous 

 pits, but where they occur among wooil fibers they are prismatic and 

 contain fewer pits. 



Crystals of calcium oxalate (conspicuous under the microscope) are 

 confined almost entirely to the cells of the wood- parenchyma fllicrs, 

 and are best observed in a tangential section, where they are occasion 

 ally solitary, but more frequently in series of a few to twenty or 

 more crystals, (Fig. 4, c.). The crystals are tetragonal or pentagonal 

 ill form and the cubical cells of the wood-parenchyma fibers containing 

 them are technically known as ideoblasts, which arc modified, thin 

 walled, wood-parenchyma cells, the cavities of which are invariably 

 I'omplelely filled with these crystalline masses. 



PITH KAYS 



.\s iilicidy noted, the pith rays (transverse section) an' scancly 

 visible to tlie unaided eye, but under the microscope appear as ijark 

 slightly undulating radial lines, which frequently bend around the 

 larger pores (Plate 111, p.r.). Pith rays (tangential section) are fnun 

 a few to fifty cells high and from one to six rows of cells wide, 

 although a good many are only from one to two rows of cells wide. 

 They vary considerably in height (Figs, o and 6) in wood of the same 

 species, but there are sufficient constant microscopic differences in 

 the rays of our walnuts to aiil in identifying the different species. The 

 cells which make up the pith rays arc rectangular in form and often 

 from one to three times as long ,is wide (Fig. 7, r.c.) ; cells in the 

 upper and lower rows are. however, more irregular in outline, often 

 being elongated in the axial or vertical direction of the stem. All pith 

 rays contain numerous simple jiits (Fig. 7. -«.p.) where they are in 

 contact with vessels and wood |iar<ni-hyma fibers. 



Analytical Key for Identifying Walnut Woods 



The following key is intemled chiefly for the use of students 

 famili.ir with the anatomy of woods and with the use of the compound 

 microscope. Lay students will, it is believed, be able to identify theup 

 woods by comparing smooth transver.se sections with the illustrations 

 and descriptions of the gross characters of the woods. An ordinary 

 )iocket ningiiifying glass will be helpful in viewing the cross-section^. 



1. JatilniiK cincrcn (I'lalf I) 



I'illi rays (tangential .section) numerous, rather niiriow (from nm- in 

 four, chlctly two cells wide), and from a few to .10 or mnrc colls liicli. 

 I'flon spntulato In outline. 



2. Jiintnni Ilium (I'lato II 1 



I'ith rays (tangential section) very numerous, liolh liroad and narrow 

 (from one to six. chiefly three in flvo cells wide), and from a fow to 2.". 

 coils liigh. spindle-shaped and olongntod olllptioal in outline. 



I'lth rays (l.ingentlal section) chiefly clonBatod-elllptical in nutlino; 

 iT.vslals of cnlclum oxalate In wood-piironehyma flbers very aiiundanl. 

 ::. .liiglan/i califomicii (Plate III) 



I'llh rays (tnngonllnl section) chiefly splndlo-shapod and Interspersed 

 among thnso elongated olllptioal in outline : crystals of calcium oxalate 

 In wood-pnroncliymn Itbors usua.Iiy wanting. 



Vossols (transverse section) numerous and rather lorgc : wood- 

 parcnebyma flbers distributod abundantly in small groups In tho early 

 wood, and irregular tangential liands of this tissue clearly visible in tho 

 late wood. 



4. Jufllans rupcstiiD (I'iate IV) 



Vossols (transvor.so section) less numerous and usually somewhat 

 smaller, especially In tho late wood : wood-parenchyma flbers less numerous 

 and distrlimtcd singly in the early woods; tangential bands of this tissue 

 loss clearly visible in the Into wood. 



