THE TISSUES OF PLANTS. 35 



(/) The trache'ids of Conifers (pines, spruces, etc.) make up very 

 nearly the whole bulk of the wood of these trees. Make a longi- 

 tudinal radial section of a pine-twig by the method employed in study- 

 ing fibrous tissue (Sohulze's maceration). Note that the tracheids 

 bear some resemblance to the wood-fibres of other wood. However, 

 their large round bordered pits are characteristic. 



(g) Make longitudinal tangential sections of the same twig. Note 

 that the bordered pits are not seen (except in section) in specimens so 

 made. 



(7i) Make cross- sections of the same twig and note that the tissue is 

 homogeneous. Compare with a similar section of an oak-twig, and 

 note the absence in the pine of the large pitted vessels which are so 

 well shown in the oak. 



(i) Make very thin longitudinal radial sections of the wood of hack- 

 berry. By careful examination tracheids may be found resembling 

 the wood-fibres, but marked with fine spirals. 



(j) Similar tracheids may be found intermingled with the wood- 

 fibres of other trees, as the maple, box-elder, elm, etc. 



