THE BEAN POD 69 



evaporation of the water, and set aside in a warm place, or merely- 

 put some pollen in sirup in a watch crystal under the bell glass. 

 Examine from time to time to note the appearance of the pollen 

 tubes. Try several kinds of pollen if possible, using solutions of 

 various strengths. The following kinds of pollen form tubes 

 readily in sirups of the strengths indicated : 



Tulip 1 to 3 per cent 



Narcissus 3 to 5 per cent 



Cytisus canariensis (called Genista by florists) 16 per cent 



Chinese primrose 10 per cent 



Sweet pea 10 to 15 per cent 



Tropceolum 15 per cent ' 



Reference. Strasburger-Hillhouse, 6 



THE EEUIT2 



47. A capsule (legume), the bean pod.' * * 



A. Lay the pod flat on the table and make a sketch of it, about 

 natural size. Label stigma, style, ovary, calyx, flower stalk. 



B. Make a longitudinal section of the pod, at right angles to 

 the plane in which it lay as first sketched, and note the par- 

 tially developed seeds, the cavities in which they lie, and 

 the solid portion of the pod between each bean and the next. 

 Split another pod, so as to leave all the beans lying undis- 

 turbed on- one half of it, and sketch that half, showing the 

 beans lying in their natural position and the funiculus, or 

 stalk, by which each is attached to the placenta. 



G, Make a cross section of another pod through one of the 

 beans, sketch the section, and label the placenta. Break off 

 sections of the pod and determine, by observing where the 



1 The sweet-pea pollen and that of Tropseolum are easier to manage than any 

 other kinds of which the authors have personal knowledge. If a concave slide is 

 not available, the cover glass may he propped up on bits of the thinnest broken 

 cover glasses. From presence of air or for some other reason, the formation of 

 pollen tube's often proceeds most rapidly just inside the margin of the cover glass. 



2 If time is not available for all of these studies, two or three types will suffice. 

 8 Material in preservative fluid such as formalin will answer, or fresh string 



beans or shell beans may be used. 



