MANIPULATION. 45 



saucers are the covered Zurich germinators, made for the purpose.* 

 These germinators, or the saucers, standing in a fiber saucer with the 

 water-bottle described in the preceding section, give an ideal germinat- 

 ing apparatus. 



If young seedlings are required, they grow excellently in chopped 

 sphagnum moss, completely freed from all lumps, in ventilated wooden 

 boxes, and these may well have a sloping glass side that they may be 

 used also for experiments in growth and geotropism of roots. An excel- 

 lent box (shown in Fig. 30) is of thin wood, 8 inches long, by 6 broad 

 and 5 deep, with a glass front sliding into a groove, and sloping at an 

 angle of about 20. The bottom has open slits and the whole is heavily 

 painted. They cost in quantity made at a box factory about 12 cents 

 each. Seeds germinate well in sawdust also (particularly if pure pine 

 sawdust be used), but I find the sphagnum much superior, particularly 

 the dead sphagnum obtained below the surface of bogs. The sloping- 

 glass so essential in observation of some physiological phenomena may, 

 however, be very simply obtained by use of a large glass funnel in which 

 the seeds may be grown, or even with a tumbler having sloping sides. 

 For most purposes the seeds are more convenient for experiments if 

 they are planted with hypocotyl pointing directly downwards. 



To Darken Bell-jars, etc. Hoods can be made from black paper 

 pinned into shape; or, very satisfactory hoods can be made from the 

 felt drying-paper used in herbaria, which is stiff enough to keep its 

 shape. It is rolled into a cylinder, a top to \vhich is made by cutting the 

 upper end into four strips, folding them inward and fastening with a 

 paper-fastener. This felt paper is a good non-conductor, and useful on 

 that account. 



To Prepare a Moist Dark-cJiamber for Germination, etc. See the 

 plan described later (on page 118). 



To Prepare a Self- or Autographic Recorder for Small Movements. 

 Wherever the movement is a direct one, and a thread may be attached 

 to the moving part, the auxanometer \vheel and cylinder later described 

 (on page 103) may be used. 



To Measure Small Downward Pressures. For this the mercury 

 flotation apparatus later described (page 124) may be used. 



To Expose Plant Parts to the Influence of Pure Colors. For this the 

 compound color-chambers later described (page 108) may be used. 



* They may be bought in this country from A. H. Hewes & Co. of North Cam- 

 bridge, Mass. , at a cost of 3 cents each. 



