MAKING A HAY INFUSION TO STUDY PROTOZOA
Materials:Driedtimothygrass (acommonwheat-likegrass called"hay"
by farmers), a fewdriedleaves, ajarofpondwatercontainingscum from the
surfaceofa pond,a smallamountof silt ormud-likesoil from thebottomof
a pond,someuncookedrice.
Follow this procedure: Fill ajar one-quarterfull of pondwater which
includes bothscum andsilt. Add a few spears oftimothygrassandseveral
leaves. Keep thejaruncoveredin a warmpartofyourhousefor a few days.
At the endofthattime, addfive or six grainsofuncookedrice to the water.
Thecombinationoftimothygrass, leaves andpondwateris called aninfusion.
You will observe:The dried grass and the leaves will begin to decay,
perhapsmakingthewaterappeara little cloudy. Morescum willappearon
the surface as time passes. Decayedpartsof the hay and leaves willdropto
thebottomofthejar. Youwillprobablynotice theunpleasantodorofdecay
thatischaracteristicofstagnantpools of water.
Theplantmatterinyourjarcontainsspores ofbacteriaof decay (see page
20) as well as some one-celledanimalsenclosed in cases called cysts. Cysts
are similar to the spores you examined in yourstudy of bacteria. Given
moistureand warmth,the one-celledanimalscomeoutoftheircysts,justas
thebacteriacomeoutoftheirsporecoats.The bacteria feed on the vegetation in the jar and cause it to decay.
Similarly, the one-celledanimalsfeed on the decayedmatter. As a result, they
grow and multiply rapidly. Some of them feed on the decaying rice grains.
As long as there is food, themicroscopicanimalsin thejarwill thrive, but they
will die as soon as the decay on which they feed is used up.
The simple, one-celled animalsliving inyourhayinfusionare known as
protozoa.