246 BOTANY. 
517. These differences in the sexual organs are accom- 
panied by similar ones in the surrounding parts. Thus 
the stamens and pistils in grass-flowers are surrounded by 
chaffy scales pale or green in color. Such flowers are 
therefore not conspicuous, although generally clustered at 
the summit of the stem. Moreover, they possess little or 
no nectar, and, with few exceptions, are scentless. In the 
Orchids there is a well-developed perianth which shows 
high specialization of form and color. Most are provided 
also with nectar-glands and an attractive odor. 
518, In Orchid-flowers the stamens and styles are fused 
together into a “column” which occupies the centre of the 
perianth. In the great majority of cases there is but one 
anther (representing one stamen), and this is on or near the 
end of the column, so placed as to be readily touched by 
an insect entering the flower. The pollen-cells cohere in 
little sticky masses, which easily adhere to the head, an- 
tenne, or back of an insect. 
519. It is an interesting fact that in the ordinary terres- 
trial Orchids the flower develops in such a way that it must 
twist upon its ovary in order to attain its proper position 
when open (Fig. 138). Thus, without twisting, the lip (J) 
with its spur would be uppermost, while the anther would 
be below. 
520. When a long-tongued insect is attracted to an 
Orchid-flower by the color and odor, it thrusts its tongue 
down into the spur (sp) in search of nectar or sweet juices, 
in the mean time perhaps resting its feet upon the lip (J). 
Its head comes in contact with the sticky discs (at A), which 
adhere tenaciously. When the insect withdraws its tongue, 
it at the same time carries away the pollen-masses adhering 
to its head. When the insect visits another Orchid-flower 
