174 



MONOCOTYLEDONS 



suited for pollination by humble-bees ; and has the three 

 branches of its style quite a noticeable distance above the free 

 parts of the three outer perianth-leaves, so that a humble-bee 

 can creep under the arms of the style. 

 The other variety of flower is adapted 

 to a long-tongued hover-fly (Rhingia 

 rostratd); and its style-arms stand so 

 close above the outer perianth- seg- 

 ments that a humble-bee cannot crawl 

 under them. Either insect visiting 

 the flower suited to it alights on the 

 reflexed portions of the outer perianth- 

 leaves ; and as it crawls under one of 

 the arms of the style, it touches with 

 its back, first the stigma, and secondly 

 an anther. It then pushes its tongue 

 down the perianth-tube, sucks the 

 honey, and finally backs out of the 

 flower. The stigma is not touched 

 by the retreating insect, because 

 it is situated on the upper face of the ledge which is 

 pushed upwards and backwards as the insect withdraws. In 

 this manner cross-pollination is ensured and self-pollination 

 averted. The flowers of the YeUow Flag again illustrate the 

 principle that the shapes of insect-pollinated flowers are to 

 be associated with the kinds of insects which pollinate them. 

 Flowers of different shapes are adapted to different circles of 

 insect-visitors. The Yellow Flag, in particular, has both "Bee- 

 flowers" and "Rhingia-flowers." 



Fig. 2ig. — Floral diagram 

 of Iris. 



Type II. : CROCUS {Crocus). 



The underground shoot is a corm (figs. 49-52). [Dig up 

 Crocuses at different seasons of the year, and observe the 

 method of development of the new corms on the old ones.] 

 The leaves are not equitant. The flowers are constructed on 

 the same general plan as those of the Yellow Flag : P3 -1- 3 

 A3 -1- G(3). The flower-stalk is short, whereas the perianth- 

 tube is extremely long. The branches of the style are not so 

 conspicuous as those of the Yellow Flag : they are band-like, 

 but aijs coiled to form tubes. 



