564 



PART III. THE CLASSIFICATION OF PLANTS. 



or small tooth-like prominences (auriculae, stelidia) on the 

 gynostemium (e.g. Orchis, Epipactis, Fig. 294 ), belonging 

 generally to the inner andrcecial whorl, but sometimes apparently 

 to the outer: in the diandrous Orchids (e.g. Cypripedium, Fig. 

 369 B} there are, generally, two fertile stamens belonging to the 

 inner whorl ; the outer whorl being only represented by an 

 anterior staminode. The anther usually has four pollen-sacs, 

 but may have two (e.g. Collabium) or eight (e.g. Calanthe, Bletia). 

 In some genera the pollen-grains are separate from each other, 

 in the majority they are united into a mass, pollinium, which fills 

 an entire pollen-sac (Fig. 294 /, F,p). The pollinium may consist 

 of tetrads with a common exine (e.g. Neottia) ; or of larger groups 

 of cells, termed massulce (e.g. Orchis), when it is said to be sectile] 

 or of uniform tissue. In those Orchids which have pollinia, 



SP I 



FIG. 369. Diagram of Orchidaceous FIG. 370. Flower of Orchis mascula ( x 2) : 



flowers, neglecting resupination. A The / the twisted ovary ; o a a the three outer 



monandrous type. S The diandrous type perianth-leaves ; i i two of the inner, I the 



(Cypripedium): the shaded stamens are third inner perianth-leaf, the labellum, with 



btaminodia. (sp] the spur ; n stigma : p pollen- sacs. 



it is frequently the case that the tissue of the pollen-sac is 

 prolonged, according to the position of the anther, either to the 

 lower (basitunnus, e.g. Ophrydinas) or to the upper end of the 

 anther (acrotonous, e.g. Phajiinae, Oncidiinae), and here almost 

 exclusively gives rise to a mucilaginous filament, the caudicle, 

 attached to the pollininm (or to the two or more pollinia of each 

 half of the anther) below or above. 



The ovary is unilocular (rarely trilocular as in some Cypri- 

 pediinae), and contains numerous anafcropous ovules on three 

 parietal placentae. In all the monandrous Orchids, the anterior 

 lobe of the trilobate stigma is not susceptible of pollination, and 

 is either rudimentary or developes into an organ termed the 

 roftellum (Fig. 294 7>), which is situated either above or below 

 the anther, and in the tissue of which one or two small masses 



