234 THE STRUCTURE OF FLOWERS 



labellum, the remaining five leaves of the perianth forming 

 together the galea or helmet. The stamens are united with the 

 style into a fleshy column or gynostemium, upon which the anthers 

 are so placed as to stand above the stigma, which is but little 

 develoi)ed, and consists usually of a large viscid surface. Of the 

 six stamens which are probably originally present, only one, less 

 often two, attain perfect development. When only one is thus 

 developed, it is always opposite the labellum ; but when two, 

 then one is on each side of the gynostemium. Only a few Orchids 

 have the pollen grains perfectly distinct ; usually they are united 

 together in fours, and these again into granular masses ; or the 

 grains are combined by a viscid fluid into a club-shaped mass 

 or polhnium within each anther lobe. Ihe two poUinia termin- 

 ate at their lower end in a pedicel consisting of the dried-up viscid 

 substance, connected together by a viscid gland or rostellum, as 

 in the Bee Orchis, or distinct, as in Orcliis aiorio." 



If we dissect a flower of the early puri)le orchis, we shall find 

 that the stigma is bilobed, and consists of two almost confluent 

 stigmas. It lies under the pouch-formed rostellum. The anther 

 consists of two rather widely separated cells, which are longitudin- 

 ally open in front : each cell includes a pollen mass or poUinium. 

 I'he polhnium consists of a number of wedge-shaped packets of 

 pollen grains united together by exceedingly elastic thin threads. 

 Below the pollen mass is the elastic caudicle. The. end of the 

 caudicle is firmly attached to a viscid button-shaped disc. Each 

 pollinium has its separate disc, which has a ball of viscid matter 

 at its under side. The rostellum lies immediately below, and the 

 balls of viscid matter lie concealed within it. Let me now try 

 to explain how this mechanism acts. Suppose an insect, say a 

 bee in search of honey, to alight on the labellum, which forms a 

 good landing stage, and to push its head into the chamber, at the 

 back of which lies the stigma, in order to reach with its proboscis 

 the end of the nectary, or what docs quite as well to show the 

 action, push a sharply pointed lead pencil into the nectary. Owing 

 to the projection of the pouch-formed rostellum, it is almost im- 

 possible to j)ush an object into the gangway of the nectary 

 without touching the rostellum. When this is effected one or both 

 of the viscid balls will almost invariably touch the intruding body. 



