Forstudyingtheotherleaves, use your hand lens. Notice how the veins
branchout from the leaf stem to all partsofthe leaf.
You will observe:In the celery leaf redcolorwillappearin definitebranch-
likestructures. The veins in the leaves of celery, as well asofoak, birch and
chestnut, move from theleafstem into a single main vein called a midvein.
Fromhere,branchingveins spread to allotherpartsofthe leaf.
However, thestructureofveins in a grass leaf differs fromthatofa celery
leaf. Notice how the veinsofa blade ofgrass are patterned in a parallel
formationfrom the leaf stemthroughoutthe leaf.
When you look at the maple leaf, you will see stillanotherintriguing
pattern. Here, the main veins seem to radiatefrom the leaf stem, much as
your fingers do from the palm of your hand. Fromthese main veinsbranches
lead to all partsofthe maple leaf.The type of vein patternthata leaf has is called "venation,"and it is
characteristicof the kind oftree on which theleafgrows. Forexample, all
oak leaves have a similar shape and the same kind ofvenation. This is also
true ofbirch leaves, maple leaves,chestnutleaves and so on. Thevenation
of oak leaves is different fromthatofmaple leaves.
Leafveinscontaina setoftubesthatconductsoil water (with its accom-
panyingminerals) from therootsand stems of theplantto all the cells in the
leaf. You know alreadythatthis water is used tomanufacturefood for the
entire plant. The veins also containa set oftubes thatconduct the food
preparedin the leaf cells to allotherpartsof theplantfornourishment.MAKING ACOLLECTION OF TREE-LEAVES
Materials:An old newspaper, several small plastic envelopes or a rollof
sticky cellophanewrappingpaper(the kind yourmotheruses in the kitchen),
cellophanetape, ascrapbookand fresh green leaves from as many different
trees as possible.
Follow this procedure: Dry or press the leaves as you did the plantsin
your fern collection. Place each leafbetween two piecesofnewspaper and
press it forabouta weekunderthe weightoflarge books. When pressed,put
it in anindividualplastic envelope or cover it with a sheetofstickycellophane
wrappingpaper.
Sortthe leaves into groups. You can classify eachaccordingto the type
of venation (above), the general shape ofthe leaf's outline or according
towhetherit issimpleorcompound. A simpleleafhas only one blade on a
leafstem. On acompoundleaf, there are many blades on a single stem. If