332 MONOCOTTLEDONES. 



which corresponds to a polleu-mother-cell in the anther, and 

 which hang together by elastic threads (Fig. 320 C, E). Each 

 polliniuni is attached at the base by a stalk (caudicle) to an 

 adhesive disc, formed by the modified stigma (rostellum), and is 

 easily liberated from it (Fig. 320 C, D, F). The pollinium, which 

 is formed in an anther-loculus, together with its caudicle and 

 adhesive disc, is termed " pollinarium " (Fig. 320 C). All 

 Ophiydete are terrestrial with tuberous roots, two of which are 

 present in the flowering period, an older one (from the preceding 

 year) containing the nourishment for the flowering-shoot of the 

 year, and a young one which is intended to contain the reserve 

 material for the following year. Inflorescence terminal. 



Orchis. The lip has a spur; each of the club-like polliuia is 

 attached to its own adhesive disc, the discs being enclosed in a 

 common pouch formed by the rostellum (Fig. 320 (7, -D). Tubers 

 ovate, undivided: O. morio, mascula ; tubers palmate : 0. incarnata, macitlata, 

 majalis. Ophrys; no spur, the two adhesive discs are each enclosed in 

 a separate pouch (Fig. 320 -F). Anacamptis and Serapias have one 

 adhesive disc. Habenaria, Gryvtnadenia, Platanthera, Herminium, 

 Nigritetta,C(Kloylossiim,etc.,ha,ve naked adhesive discs (no rostellum). 



5. EPIDENDRE.E. Acrotonous Orchids with deciduous anthers (except 

 Mida.ris) ; 2-8 wax-like pollinia, with or without caudicles ; generally no 

 adhesive discs. Malaxis (the flower is twisted through a complete circle, causing 

 the labellum to be turned upwards), Sturmia and Corallorhiza ' (Coral-root) ; 

 the latter has a creeping, coral-like rhizome witnout roots, and is destitute of 

 chlorophyll except in the ovary. The other two somesvhat resemble the 

 tropical Orchids in having the lower interuodes of the axis of the inflorescence 

 tuberous. Liparis; Calypso. Most of the genera are tropical epiphytes and 

 many have aerial, green tubers formed from one or more steru-internodes ; 

 Dendrobium, Eria, Pliains, bletia, Epidetidrum, Cattleya, Ltdia, Pleurothallis, 

 Jiestrepia, Masdevallia, Bitlbopliyllum, etc. 



6. VANDE.E. These resemble the preceding but have only 2 wax-like pollinia 

 in each anther, which are attached by a caudicle to the adhesive disc <>f the 

 rostellum. Nearly all are tropical epiphyte?. Stanhopea, Catasetuin,Maxillaria, 

 Oncidiiim 1'andn, Polystachya, etc. 



6,000 (10,000 ?) species. The majority live in the Tropics and occur, es- 

 pecially, as epiphytes on trees or in the crevices of rocks, to which they are 

 attached by aerial roots. These aerial roots, like those of Aracea?, are covered 

 by several layers of spirally-thickened cells (tracheides) which contain air 

 and form the velamen an apparatus to absorb moisture from the air. The 

 roots have a white appearance when the cells are filled with air, which 

 changes to a greenish hue when they are tilled with water, the chlorophyll 

 then shining through. They generally have horizontal rhizomes ; the 



1 Corallorhiza = Coralliorrhiza. 



