HYPOGYNOUS MONOCOTYLEDONS 



199 



grains with their markings are always alike in the same 

 species, so that it is possible to recognize a plant by its 

 pollen alone. These characters are generally too minute 

 to be observed without a compound microscope, but in 

 the hibiscus, and some others of the mallow family, they 

 can be distinguished with a hand lens. 



285. The Pistil. Remove the stamens and sketch the 

 pistil as it stands on the receptacle. Label the round or 

 oval enlargement at the base, ovary, the threadlike append- 

 age rising from its center, style, and the tip end of the 

 style, stigma. If the stigma is lobed or parted, count the 

 divisions and see if there is any correspondence between 

 them and the number of petals and sepals, or of the lobes 

 of the ovary. Examine the tip with a lens and notice the 

 sticky, mucilaginous exudation that moistens it. Can you 

 think of any use for this ? If not, touch one of the pow- 

 dery anthers to it, and examine it again with the lens. 

 What do you see ? t 



286. Pollination, or the transfer of pollen from the 

 anther to the stigma, is a matter of great importance, 

 as the pistil can not develop seed without it. Note the 

 relative position of pistils and stamens and see if it is 

 such that the pollen can reach the stigma without external 

 agency. 



287. The Ovary. Observe 

 the shape of the ovary, and 

 the number of ridges, or 

 grooves that divide the sur- 

 face. These lines correspond 

 to the sutures of the fruit, and 

 show of how many carpels the 

 ovary is composed. In the 

 star-of- Bethlehem the ovary 

 has six sutures, three of which 

 represent the midrib of the 

 carpellary leaves, and three 



382, 383. Ovary of yucca aloifolia, 

 a hypogynous monocotyledon, dis- 

 sected : 382, vertical section : ov, 

 ovules; 383, diagram of a horizontal 

 section of the same, enlarged, show- 

 ing the three carpels and six cells, or 

 loculi : ds, dorsal sutures ; vs, ventral 

 sutures ; ov, ovules ; //, placenta. 



