162 SYSTEM OF DECANDOLLE. 



When the organization of the stem may be doubtful, 

 we have the ternary type in the floral structures ; if the 

 quarternary type should be seen, we have the parallel 

 venation and monocotyledonous embryo, etc. 



CRYPTOGAMIA. 



Stems analogous to those of plants in general, not al- 

 ways existing, when existing may have true woody 

 matter in the form of variously (often sinuous) shaped 

 bundles running down within it, or may consist of cel- 

 lular tissue alone. Leaves or foliaceous expansions, 

 when existing, having their veins dichotomous, or des- 

 titute of them entirely. Flowers (as generally under- 

 stood by the term) not present. Sexual organs not dis- 

 tinct, or not stamens and pistils, producing no embryo 

 but multiplying by sporules. 



The following examples will show the student the 

 deviations that may exist in plants from a general cha- 

 racter found existing in their allies. Among the Exo- 

 genee, some of the Coniferse have from two to ten co- 

 tyledons, Schizopetalon Walkeri, a cruciferous plant, 

 has four, and Cuscuta has none at all ; the Ranuncu^ 

 lacese may have the sepals and petals developed upon a 

 ternary type ; Nepenthes has no concentric zones or 

 medullary rays ; the Peppers have woody matter in 

 the form of bundles, and Phytollacca dioica is destitute 

 of liber. Among the Endogena, two cotyledonary bo- 

 dies may be seen in Triticum ; the scales of the single 

 floral covering in Potamogeton are developed upon a 

 quarternary type ; a reticulated system of venation may 

 be seen in the leaves of Arum maculatum, and a corky 

 bark upon the rhizoma of Tamus elephantipes. Never- 

 theless, as " the differential signs of natural associations 



