A MANUAL OF BOTANY 149 



What shape has it in section ? Examine the surface (m) 

 for dotlike markings (stoniates). Are there few or many 

 of these? Where are they distributed and how are they 

 arranged ? What color has the mature leaf? If possible, 

 compare it with the young leaf for form, size, and color. 

 Examine a leaf in cross section (Ip) and look for the outer 

 epidermis, much thickened, the central vascular bundle, and 

 the meaophyll containing resin ducts or small openings in the 

 outer portion. Carefully study each region and determine 

 the character of the cells and their arrangement. What 

 use has each of these features of the leaf ? Observe the 

 palisade cells (or the outer layer of mesophyll). How are 

 the cells arranged with reference to the epidermis ? What 

 are the advantages of such an arrangement ? 



Stem in section. Examine a section of a young stem. 

 The layers from outside towards the center are the bark, 

 ivood, and pith. Seek for resin ducts in the bark. Observe 

 the sticky cut end of the twig and test its odor. Study, if 

 you have them at hand, thin sections of pine wood, cross 

 and long, observing cells and their peculiar form and mark- 

 ings. Examine pieces of white and yellow pine lumber, 

 and find the difference in color, tceiyht, grain, and hai'dness. 

 Which would be the better lumber for various building pur- 

 poses ? Read about pine lumber and find all the many 

 uses of the different species that time will permit. 



Staminate inflorescence "blossoms." Examine the fresh or 

 dried specimen of the staminati'. inflorescence (sporophylls) 

 of the pine. Where is it located with reference to the old 

 and young leaves, and of what is it composed ? Examine a 

 single part (cone of sporophylls) and observe the scales 

 (microspoi'ophylls) composing it. Remove the scale (m) 

 and find the receptacles containing the yellow powder {pollen 

 or microspores). What name would you apply to the recep- 

 tacles ? Examine pollen {hp) and observe all its peculiari- 

 ties. What do you Hnd out about the number of pollen 



