182 Elementary Botany 



and the pencil comes in contact with the viscid substance at 

 the base of the poUinia. On removing the pencil one or both 

 of the pollinia are removed attached to it. It will be found 

 after removal they gradually bend over towards the point of the 

 pencil. 



If an insect, such as a bee, visits the plant for the honey 

 contained in the spur, it presses its head against the rostellum, 

 and flies away with the two pollinia attached ; on visiting a 

 second flower these have bent forward, so that instead of re- 

 turning to the same place from which they were taken in the 

 previous flower, they strike against the viscid stigma, and some 

 of the pollen remains attached. 



The exact method of fertilisation varies in the different 

 plants of this order. It is very widely diitributed, especially 

 in tropical regions. Many of the plants are epiphytes, or air 

 plants : clinging to the trunks of trees, their roots are green 

 with stomata, and never reach the soil ; they absorb all their 

 nourishment from the air. Many of the plants are remarkable 

 for the singular shapes of their flowers, which simulate various 

 natural objects, insects, birds, reptiles, &c. So much so that 

 Dr. Lindley says, ' So various are they in form, there is scarcely 

 a common reptile or insect to which some of them have not 

 been likened.' Amongst our British genera we have the Fly 

 Orchis {Ophrys ?nusdfera), which presents the appearance of 

 several flies growing up the stem ; Bee Orchis {Ophrys apt/era) 

 and Spider Orchis {Ophrys aranifera), each with the flowers 

 like the insects named. There are various species of the genus 

 Orchis, all of which have spurred flowers : Aceras, or Man 

 Orchis (fig. 314, I.) ; Listera, or Twayblade ; Habenaria, or 

 Butterfly Orchis, and others. Though so numerous a family, 

 the plants are not economically useful. Salep is a starchy 

 esculent substance obtained from the roots of several species 

 of Orchis ; and vanilla is a flavouring material obtained from the 

 fruit of an exotic plant. Vanilla aromatica. The marvellous 

 forms of the flowers cause them to be much cultivated in our 

 greenhouses. 



