204 



THE FLOWER 



391. Cross section of 

 ovary of iris flower : c, c, car- 

 pels ; /, /, cells, or loculi ; ov, 

 ovules ; //. placenta. 



parietal (Sees. 103, 109). Draw a cross section of the 

 ovary ; how many cells has it ? Examine with a lens the 

 little flap under the two-cleft apex of one of the stigmas, and 

 look for a moist spot to which the 

 pollen will adhere. Label this in 

 your longitudinal sketch, stigmatic 

 surface. No seeds can be matured 

 unless some of the pollen reaches 

 this surface ; can you think by what 

 agency it is carried there? What 

 insects have you seen hovering 

 about the iris ? Notice that in draw- 

 ing his head out of the flower, an 

 insect would not touch the stig- 

 matic surface, since it is on the upper side of the flap and 

 he would be probing tmdcr it. But in entering the next 

 flower that he visits, he is likely to strike his head against 

 the flap and turn it under, thus dusting it with pollen 

 brought from another flower. 



Sketch a sepal and a petal separately, and note their 

 differences as to shape, color, and texture. Hold each up 

 to the light and observe the veining. If this is not clear, 

 stand a specimen in red ink for two or three hours and 

 examine it again. Is it parallel or net veined ? Can you 

 think of a use for the crest of hairlike filaments on the 

 upper side of the sepals ? 



Examine a bud in cross section. Notice how the sepals 

 and petals overlap, and draw a diagram of the section. 

 This manner of arrangement, where the 



outer edge of one piece covers the inner edge 

 of the one next above it (Fig. 387), is said to 

 be convolute. Draw diagrams showing the 

 horizontal and vertical arrangement of parts 

 in the iris. What is its numerical plan? 

 Is it symmetrical ? Regular ? Are the parts 

 all free? If not, which are united among 



themselves or with other sets of organs? 

 above or below the other parts ? 



302. Horizon- 

 tal diagram of iris 

 flower. 



Is the ovarv 



