DICOTYLEDONS: POLEMONIALES. 695 



The leaves are rounded, crenate on the margins, the lower 



ones petioled and heart-shaped, and 



the upper ones sessile and clasping 



around the stem beneath the flower 



clusters. From the clasping character 



of the upper leaves the plant derives 



its specific name of amplexicaule. The 



, , . Fig. 584- 



plant OCCUrs in waste places and IS Diagram of Lamium flower. 



rather common. 



SUGGESTIONS FOR STUDY OF A LABIATE FLOWER. 



1183. The catnip (Nepeta cataria). While the "dead-nettle" is used 

 here to illustrate the mint family, other species may be studied instead. 

 The exercise is written for the catnip (Nepeta cataria), a very common 

 weed occurring from July to September. If fresh material is not at hand 

 when the study is made, dried entire plants, and the flowers, in formalin 

 may be used, unless it is preferred to use fresh material of some other 

 available species. In that case the dead-nettle here illustrated, and the 

 outline, will serve as a guide for the study. 



The entire plant. Note the habit, the character of the branching, the 

 shape of the stem, the character of the surface. Note the form and arrange- 

 ment of the leaves. Is the plant annual, biennial, or perennial? 



The inflorescence. What is the inflorescence? The flower: the parts 

 present; the calyx, form and relation of parts; the corolla, form, relation 

 of parts, into what two parts is the corolla divided, the name of the two 

 parts, the number of petals in each part, Note the stamens, number, 

 size, position in the flower. The pistil; sketch a pistil showing the nutlets, 

 the long style. 



To study the stamens remove a corolla, split it open down one side and 

 spread it out on a glass slip and mount in water; or pin it to a cork. Ex- 

 amine with a good hand lens, or with the lower power of the microscope. 



Construct the floral diagram. 



Cross -pollination by insects. Study the adaptations of the flower for 

 this purpose. The lower lip is the landing place, and the upper lip is the 

 "banner." If there are color markings on any portion of the flower which 

 serve to guide the insect in entering the flower, describe them and note the 

 location. With a needle imitate the entrance of an insect into the flower 

 and determine the way in which cross-pollination takes place. 



Compare if possible other members of the mint family in the study of 

 cross-pollination. 



Material. Entire plant with flowers and ripe fruit. If fresh plants are 



