I04 



CELLULAR TISSUE. 



walls. The other part of these cells however becomes expanded to form a great oval 

 bladder which intrudes deeply into the sub -epidermal parenchyma. As soon as the 

 processes of expansion and division in the neighbouring cells begin, there grows from 

 the middle of the thickened outer wall, perpendicularly into the interior, a peg-shaped 

 process (consisting of cellulose), the blunt end of which swells into a knob {£). 

 When the leaf is fully developed {E) the swelling has the form of an egg-shaped or 

 almost spherical body, which attains a size filling half or more than half of the cell. 

 This is the cystolith, which is thickly covered on its exterior with pointed and blunt 

 radially diverging conical warts, and is suspended in the cavity of the bladder-like 

 cell by an irregularly cylindrical stalk, which is continuous directly into the original 

 thickened outer wall. The whole body is impregnated with calcium carbonate, and 



FIG. 44.— FicLS elastica ; leaf, transverse section, e—e in earli ^=c. tl,« .f i 

 side i W , (390) nnder side of tire same very young leaf'l^ A an °,lr^,H ""f''''^^ "f "-e epidermis ; A (600) npper 

 and a Hair (transient) ; in A two cystolith-eellsfrecoinisabie hv fh!r7,v '?'' I ='°°"'' ^'''"^ "'""'"^ superlieial, 

 undivided.-^ (600) npper, B, (300) under side of a r«W ^M , '"'".?"=''="'='' <"'«=■• "all, epidermal cells- as yet 

 a younger and ., an oL^ sAgT^:ZsSSS,^ii^^',^^^'\^'' 'P'^="°=l cells undargoi„B divUion. In J, i is 

 leaf, under side ; division of the now three-layered^tJder^Ts if * J^ w •^''"?«»« "f ^e waU.-C (390) older 

 and form Of the parts is notyet attained.-. u^ppersTd'/^J^'^a^t^^TSIoir^^^^^^^^^ 



the stalk also with silica: it has a homogeneous glassy appearaiice, and in the pointed 

 warts there is often stratification and granulation. Acids dissolve the calcium salt,- 

 bubbles of carbonic acrd being produced. After solution the stalked body remains 

 behmd with Its ongmal attachment; the stalk is but little altered, the swelling re- 

 mammg as a delicate cellulose skeleton, the outline having become more irregular: 

 the interior shows well-marked stratification and delicate radial striation, the layers 

 from the end of the stalk onwards being nearly concentric with the surface. 



