Table 1.

Comparison of floral secretory tissue in investigated taxa

Character	Gomesa longipes (Lindl.) M.W. Chase & N.H. Williams	Vitekorchis excavata (Lindl.) Romowicz & Szlach	Oncidium heteranthum Poepp. & Endl. var. album	Cyrtochilum meirax (Rchb.f.) Dalström
Position and type of elaiophore	Callus Intermediate	Callus Intermediate	Callus Intermediate	No obvious elaiophore Oil-like, but seemingly less viscid and more volatile
Appearance of secretion	Wax-like and heterogeneous	Wax-like	Oil-like
Type of secretory tissue	Cuboidal epidermal cells, trichomes and papillae	Cuboidal epidermal cells, trichomes and papillae	Cuboidal epidermal cells, trichomes and papillae	Cuboidal epidermal cells
Secretory residue visible under SEM	+	+	Fertile flower + Sterile flower –	–
Type of epidermal cuticle	Smooth	Striate	Fertile flower Striate Sterile flower Smooth	Finely striate
Cuticular blisters	–	–	Fertile flower + Sterile flower –	–
Subcuticular accumulation of secretion	+	–	Fertile flower –	+
Cell wall protuberances	–	+	Fertile flower –	–
Secretion or vesicles present in wall or periplasmic space	+	+	Fertile flower +	–
Endoplasmic reticulum	Mainly SER	Mainly SER	Fertile flower Mainly RER	Mainly RER
Plastids	Amyloplasts with starch, plastoglobuli and poorly developed internal membranes	Amyloplasts with starch, plastoglobuli and poorly developed internal membranes	Fertile flower Amyloplasts with starch, plastoglobuli and poorly developed internal membranes, but also chromoplasts Sterile flower Amyloplasts as above	Amyloplasts with starch, plastoglobuli and poorly developed internal membranes, but also oil-laden elaioplasts
Cytoplasmic lipid droplets	+	+	Fertile flower + Sterile flower +	+, but also irregularly shaped osmiophilic bodies
Intravacuolar membranes	Myelin-like figures present	Membranous enclaves, but highly organized myelin-like figures absent	Fertile flower Membranous enclaves, but highly organized myelin-like figures absent Sterile flower Myelin-like figures absent	Myelin-like figures absent