396 



SYSTEMATIC BOTANY. 



Fig. 480. 



Fig. 480. Calla: spathe and spadix. 



Fig. 481. Amorphophallits : corm, spathe, and spadix. 



ILLUSTRATIVE GENERA. 



Subord. 1. ARACEJE. Flowers 

 imperfect ; spadix surrounded by a 



Arum, L. 

 Colocasia, Ray. 

 Caladium, Vent. 

 Dieffenbachia, Schott. 

 Bichardia, Kunth. 



Subord. 2. OROXTIACE^:. Flowers 

 perfect, mostly witJt, a perianth ; spa- 

 dix surrounded by a spathe or naked. 

 Tribe 1. With a spathe. 

 Calla, L. 

 Pothos, L. 



Tribe 2. Without a spathe. 

 Orontium, L. 

 Acorus, L. 



By Engler this large group has been recently subdivided into ten sub- 

 orders and numerous subsidiary tribes and subtribes. The suborders are 

 Pothoideaa, Monsteroideae, Lasioidese, Philodendroidese, Aglaonemoideae, 

 Colocasioideae, Staurostigmoidese, Aroideae, Pistioideae, and Lemnoideae. 

 The principal characters relied on to distinguish these groups are the 

 presence or absence of laticiferous vessels, the presence or absence of H or 

 H shaped intercellular hairs, the arrangement of the leaves and shoots, 

 the venation of the leaves, the bi- or unisexual flowers, the presence or 

 absence of a perianth, the direction of the ovules, &c. &c. 



The floral formula for Acorus is P '. + .'. A .'+" Gv, the ordinary 

 Monocotyledonous form. In other genera great modifications arise from 

 suppression of parts, &c. 



Affinities, &c. The peculiar thickened fleshy flowering stem densely 

 covered with flowers of rudimentary structure, forming the spadix of this 



