Vegetative Organs of Vascular Plants 743 



SclagineUa has highly localized distribution, but excellent 

 preserved material is obtainable from dealers, and several species are 

 extensively cultivated in greenhouses. The processing is the same as 

 for Lyco podium, the infiltration must be slow and thorough, because 

 the stele is literally suspended in a highly parenchymatous cylinder 

 and is easily torn in cutting. 



The vegetative organs of Isoetes are studied only in advanced work 

 in anatomy, and there is comparatively little demand for slides. Roots 

 should be severed and divided into short pieces. The compact stem 

 and rhizophore may be processed entire or quartered. The methods 

 used for Lycopodiiim are satisfactory. The highly silicified stem of 

 Equisetiim has long been a problem for technicians. Penetration is 

 diflicult with an aqueous killing fluid, but FAA is satisfactory. The 

 older stems must be desilicified by treating with hydrofluoric acid. 

 Transfer directly from FAA to the acid diluted with twice its volume 

 of 95 'v alcohol. After 2 days in acid, wash in 50% alcohol, making 

 at least five changes at 4-hr. intervals. Observe the precautions 

 concerning the use of HF given in Chap. 8. Dehydrate in TEA, and 

 infiltrate slowly and thoroughly. Rhizomes and roots do not need 

 to be desilicified, otherwise the processing is the same as for aerial 

 stems. 



The Leaf 



The mesophytic dicotyledonous broad leaf is the type most 

 commonly used for the study of the so-called typical leaf. Some general 

 directions apply for the handling of most types of leaves. Leaves are 

 easily damaged during processing by apparently minor mishaps. It is 

 therefore desirable to kill duplicate batches in each of the formulas 

 used, keeping one batch in the preserving fluid while the other one 

 is embedded and tested. Consult Fig. 2.1 concerning the usual 

 methods of subdividing leaves. Good results can be obtained with 

 many leaves by killing in FAA. Soft leaves having small veins can be 

 dehydrated in acetone or ethyl alcohol, whereas leathery leaves, or 

 leaves with thick or wiry veins should be processed in butyl alcohol 

 or dioxan. One batch of each subject may well be killed in FAA and 

 another batch in one of the fluids given in the following specific 

 recommendations. 



The firm leaves of the trees and shrubs are represented by apple, 

 cherry, rose, lilac, and privet. Leaves of apple and related plans may 

 be killed in FAA, but occasional batches exhibit considerable 

 plasmolysis (Fig. 11.1). Consistently good results can be obtained 



