248 



HARD WICKE 'S SCIENCE- G OSSIP. 



part in vegetable physiology, in connection with the 

 bast-cells': these may bfc found in the phleum of the 

 lime, but it is more easily traced in the stem of the 

 vegetable -marrow or cucumber ; either of which may 

 be procured at almost any season of the year. We 



and 4 the epidermis. Now examine 2 with a higher 

 power (see fig. 173 : sieve-plate), the sieve-plate will 

 be found in the transverse^section ; then notice the same 

 in a longitudinal section — it is seen to be composed of 

 spiral vessels, surrounded with a thickened wall. Our 



Fig. 169.— Transverse section of Pine-stem. 



Fig. 171.— Transverse section of leaf of Pine. 



^Mm^ 





Fig. 172. — Transverse ."section of stem of Cucumber. 



r' 3 4- 5 



Fig. 170. — Longitudinal section of Pine-stem. 



now refer especially to the sieve-tubes and sieve-plates. 

 (See fig. 172 : transverse section of part of the stempf 

 cucumber.) No. I, i is hard-bast or bast fibres — 

 tliis is darker in appearance than the cells adjoining 

 No. 2, or sieve-tube ; 3 is succulent ground tissue ; 



Fig. 174.— Suspensor of the Shepherd's-purse. 



object is to simplify the lessons, hence we do not give 

 a detailed description of the form and economy of the 

 sieve-tubes — it would occupy too much space ; besides, 

 it is entered into fully in the volumes previously re- 

 commemded. 



