154 PRACTICAL COURSE IN BOTANY 



2. How would you distinguish between a chinquapin, a chestnut, a 

 chestnut oak, and a horse-chestnut tree by their leaves alone ? By their 

 bark and branches ? Between a hickory, ash, common elder, box elder, 

 ailanthus, sumach ? Between beech, birch, elm, hackberry, alder ? 



(Any other sets of leaves may be substituted for those named, the object 

 being merely to form the habit of distinguishing readily the differences 

 and resemblances among those that bear some general likeness to one 

 another.) 



3. From the study of these or similar specimens, would you conclude 

 that resemblances in leaves are confined to those of closely related kinds ? 



4. Name some causes independent of botanical relationship that might 

 influence them. (169, 170; Exps. 48, 57.) 



5. Do you find, as a general thing, more leaves with stipules or without ? 



6. Is their absence from a mature leaf always a sign that it is really 

 exstipulate? (166.) 



7. Can you trace any line of development through intervening forms 

 from a merely sessile leaf, like that of the pimpernel or specularia, to a 

 peltate one ? (Figs. 184-187, and observation of living specimens.) 



8. Does the leaf determine the position of the node, or the node the 

 position of the leaf ? 



9. Strip the leaves from a twig of one order of arrangement and replace 

 them with foliage from a twig of a different order; for instance, place 

 basswood upon white oak, birch upon lilac, elm upon pear, honeysuckle 

 upon barberry, etc. Is the same amount of surface exposed as in the 

 natural order ? 



10. What disadvantage would it be to a plant if the leaves were arranged 

 so that they stood directly over one another ? (169.) 



11. Why are the internodes of vigorous young shoots, or scions, gen- 

 erally so long ? (150.) 



12. If the upward growth of a stem or branch is stopped by pruning, 

 what effect is produced upon the parts below, and why? (152, 153.) 



13. Give some of the reasons why corn grows so small and stunted when 

 sown broadcast for forage? (60, 63, 169.) 



14. What is the use of "chopping" (i.e. thinning out) cotton? 



II. THE VEINING AND LOBING OF LEAVES 



MATERIAL. Leaves of any monocotyl and dicotyl will show the dif- 

 ference between parallel and net-veining. To illustrate the palmate and 

 pinnate kinds, the leaves of grasses and arums may be used for monocotyls, 

 and for dicotyls, those of ivy, maple, grape, elm, peach, cherry, etc. ; for 

 division, examine lobed and compound leaves of as many kinds as are 

 attainable. A specimen showing each land of veining should be placed in 



