MS 



aiCNKllAI, ftTRUCTUUli OF HOOT AND ,STI':i\l 



rays now ii|)ponr iis iniri'ow lines. Tluit is, we now sec I lie cdfjos of tlic 

 bliidc'S wlioso sidos weir IjcIopo seen. I'lissing onlwiird licyond liic 

 last of liio atuuial rinj!,s, wliicli sn('('('ssi\'("ly cxliiliit a. Rrcalcr innnbor of 

 wood-hundlfs and nu'dnllary rays, we roach (he canihinni-i'in^f. Onlsidr 

 of tliis we lind (lie |)liiocnior hast hundlcs scijaratcd l)y medullary rays 

 C'ontinnons witii (hose of Ihc wood cylindoi-, and still onlsidc of (his the 

 l)eriderni. 



a 



c 

 c 



423 



I''ig, 423. DijiKi'iini illiiHl,nil,inK Hi'cl-idii nf wdixly iini-iinn oT (li(iol,\liMlniinMH Mloin: a, oiIkch (tf tni-diil- 

 Iiiry ray« uh Hccn in (,riinHV)irMO hcc l,ii,n ; /», HiilcH (if hmiihmih hi-imi in I'lidilll hci'I inn; c, (mkIh lis thi'.v wuuld 

 lippuur in UmKnnlJul MOiiUitn. 



Jlipcaravrr. oj the Tdiij/C'idial Sccliaii. 'V\\v a|)|)ea.ran<'c of a (ani^'cn- 

 tiiil scclion will (U^pend, of conrse, njxin (he (issues throu).,di which it 

 j)a,sses. If it cuts the medullary rays these will a])pear neidier as the 

 hroad sides, as a( b, nor the edfjes of ])lades, as a( a, hut as (rans\'erse 

 stH'tions of them, as a,( r. IT the ray consists of l)n( one row of cells in 

 width, then such a. row will he exhihited n])oii the (angential section, its 

 vertical hcnffhl varyinj; from a very few to (piite a lar^;e number of cells, 

 ir, upon th(^ othtw hand, it possess a, lateral breadth of several thiek- 

 ne.sses of cells, of f) in our (ifjure, this condition will exist (Uily at its 

 middl(! portion. At its U])i)er and lower limits it will ordinarily be 

 reduced l<i th(\ thickness of a sin>,de cell, so that the tangential aHi:ect 

 of a medullary ray is almost always thai of an clli|)se, broad or narrow, 

 according t,o tlu^ number of rows of cells of which it consists, in contrast 

 with tin' extent of its u|)ward and (low nward extension. 



