SPERMATOPHYTES— ANGIOSPERMS 



353 



The leaf. — Young and tender leaves should be fixed in formalin 

 alcohol and out in paraffin. Cut sections freehand whenever there is 

 sufficient rigidity. Resort to pith only when necessary. In cutting sec- 

 tions of a leaf like that of Lilium, lay one leaf on another until you 

 have a bundle of them which will be nearly square in transverse sec- 

 tion. Wrap the bundle with string for about 15 mm.; cut the bundle 

 transversely so that about 5 mm. of the bundle will project beyond the 



Fig. 123. — Sparganium eurycarpum: photomicrograph of transverse section of young root; 

 fixed in chromo-acetic acid and stained in Bismarck brown; Cramer contrast plate; 16-mm. objec- 

 tive; ocular X4; no Abbe condenser; yellowish-green filter; camera bellows, 1 meter; exposure, S 

 seconds. X90. 



tied portion. Dip in melted paraffin, as already suggested for Pinus, 

 fasten the tied portion in the shding microtome, and cut with the 

 knife placed obliquely. About 15-20 n'lSSi good thickness for general 

 leaf structure. In case of large leaves, cut out pieces 1 cm. wide and 

 3 cm. long and tie them together to make a good bundle for cutting. 



For the finest preparations, imbed in paraffin. The common Hlac, 

 Syringa, has a good leaf to illustrate palisade and spongy parenchy- 

 ma : the privet, Ligustrum, is even better. Ligustrum japonicum has 



