36 



BOTANY. 



F 



^ 



B 



thin partition, thouglit that the lenticular cavity was formed by the 

 separation of the walls of the two contiguous cells at that place, and con- 

 A , Bequently that tliey were 



"~ ' intercellular. This in- 



terpretation is still given 

 in some hooks.* 



31. — While the 

 bordered pits of the 

 ConiferEe are neTsr 

 crowded together, in 

 the cells of some 

 plants they are so 

 numerous as to lie 

 closely side by side 

 (Fig. 17). In such 

 case the first thick- 

 ening of the wall pre- 

 sents itself as a net- 

 work of ridges en- 

 closing elliptical thin 

 places. As the thick- 

 ening advances the 

 ridges increase in 

 height, but at first 

 not in breadth ; later 

 they increase in 

 breadth at the top and 

 overarch the thin 

 areas, much as in the 

 bordered pits of the 



transverse eection of mature wood ; ;7i,'cetitral layer p,-.T,:-Po««i T-n +Viio 



of ihe common wa'l; <, a mature pit cut through tbe ^.^Olllieice. xu uuio 

 middle ; t', the pame, hut in a thiclcer part of the sec- nn^n limvpvpr +bp 

 tion, the pan of the cavity of tne pit seen in perspec- ^"^^i liuwcvci, uiic 

 tlvc ; t", a pit cut tlir.ugh below its openings; B, rinonino' 1+ thp ton of 

 transverse section through the camhiura;c,camT)iim; Openmg at Ttie TOp Oi 

 A, very young wood-cells : t, t, very young bordered fjjg -^{1 jg oji eloUffat- 

 pits, seen in secti.m ; C, diagram of sectional and lat- ^"" F"' '° '^ ciu±jgti,u 

 eral views of a young bordered pit; D, diagram of 0(J g\[\^ instead of a 

 sectional himI lateral views of a mature bordered pit : . . 



£, section of a mature pit, seen in perspective ; F, circle (Fig. IVj -4, 

 section of a younger pit seen in perspective. A and n ^ \ mi 1 1 ■ 



B X BOO.— After Sachs. and C, t). The thin 



plate separating opposite bordered pits of this kind breaks 



* See Le Maout and Decaisne's " Trait6 Generale de, Botaniqne," 1868 

 [English edition, 1872] ; (iriffitli and Heufrey's " Micrographic Die- 



