APPARATUS AND MATERIALS. 37 



2 bell-jars, 15 by 30 cm. inside diameter, preferably with ground- 

 glass stoppers and ground-glass edge, with ground-glass plate to cover 

 bottom. 



2 upright test-tubes or equivalent, 

 i small test-tube. 



i battery-jar (see page 78). 



A 3-inch slide with a slight smooth hollow. 



A germination-box (see page 117). 



i large fibre saucer (see page 108), useful for many purposes. 



Nest of ten beakers. 



3 or 4 cheap wooden millimeter scales 30 cm. long (costing about 3 

 cents each from educational supply companies). 



5 Soyka flasks for chlorophyll and color screens. 



D. PLANTS. 



Following are amongst the most useful plants for physiological study : 



Sphagnum moss, obtainable in most bogs, and usually kept for use in 

 greenhouses. It may be bought in bales (for about $1.50 per cubic 

 meter) from dealers in seeds and greenhouse supplies. The dead moss 

 obtained from below the surface of bogs is much better for germination 

 experiments than the surface living layers. 



Seeds of beans. Horse-beans (Vicia faba equina) are best ; they grow 

 vigorously, are little liable to mould, and do not elongate the hypocotyl 

 and raise the cotyledons in germination, a point of much importance in 

 most experiments on geotropism. Windsor or broad beans (Vicia faba) 

 are also good, but germinate more slowly. 



Tradescantia for protoplasm in stamen-hairs. Tradescantia virginica 

 is best, but blossoms in spring and summer. It may be kept in blossom 

 and in condition for use in September, October, and November by cut- 

 ting the plants back to near the ground before they blossom in June, 

 when they will come up again and blossom in the fall. If surrounded 

 by a frame and covered by a sash on cool nights, they may be kept in 

 good condition up to the end of November. Tradescantia zebrina, the 

 Wandering Jew, grown in nearly all greenhouses, and blossoming most 

 of the time, is nearly as good. But the hairs of gourds may be used 

 instead (see page 51). 



Nitella, for protoplasmic movement, etc. May be kept in good con- 

 dition in large dishes in the greenhouse all winter; must not be given 

 too much light. Chara is nearly as good. 



Ricinus, for absorption, root-pressure, etc., should be planted and 

 raised into 4-inch pots four weeks before needed. 



Tropseolum majus, the Garden Nasturtium, should be propagated 



