SEEDAGE 



jected; also if 1 per cent or more of weed seeds i>,- 

 found. 



The reference collection of seeds should be kept in 

 neatly labeled glass bottles, without necks, tightly 

 stoppered and systematically arranged in shallow pasi,~- 

 board boxes (see Fig. 2295). A convenient size for these 

 bottles is 2 iu. long by 3-5 in. in diameter. A tray 

 holding 100 of such bottles should fit into an ordinary 

 herbarium case. If the collection'is large, a card index 

 will be of great assistance in finding the specimens. 



Germination Testa. The seeds used in germination 

 tests must be taken indiscriminately from pure seed 

 which has been thoroughly mixed for that purpose. 

 The selection of plump, nice-looking seeds for these 

 tests, as frequently practiced, impairs the authenticity 

 of the result. 



Tests may be conducted in the laboratory between 

 damp cloths or blotters, or in porous saucers, or iu sand 

 or soil in a greenhouse. Seeds which are known to ger- 

 minate with difficulty should be tested in a greenhouse 

 as well as in the laboratory. The same is true of any 

 species of seed whose conditions of germination are not 

 well understood. 



While damp blotters serve as the best substratum 

 under ordinary circumstances, and especially where a 

 large number of tests are to be made, they do not 

 answer as well for fine, slow-germinating seeds like 

 tobacco and June grass, and many flower-seeds, owing 

 to the fact that the blotters sometimes adhere too closely 

 to permit the proper circulation of air. This may be 

 remedied to a certain extent by placing narrow strips of 

 glass between the folds, but main reliance in such cases 

 should be placed upon soil tests. 



All tests are to be made in duplicate, using two lots 

 of 100 seeds each of peas, beans, corn, cucurbits and 

 others of a similar size, and 200 seeds of clover, cab- 

 bage, lettuce, etc. The more seeds taken for test the 

 less the chance of error. However, 5 per cent to 10 per 

 cent of variation may be expected between the two lots 

 of seed, even though they might have been taken from 

 the same plant. In the case of a greater variation than 

 10 per cent the test should be repeated. Seeds upon 

 which moulds form quickly are likely to be old stock. 



The seeds should be inspected daily, a note being 

 made of those having sprouted, which are then thrown 

 out. In testing seeds of the pea fam- 

 ily (Leguminosse) one-third of those 

 remaining hard and fresh at the close 

 of the test are usually counted as hav- 

 ing sprouted. The average of the 

 duplicate tests is to be taken as the 

 percentage of vitality. Averages 

 should not be made, however, between 

 results obtained by different methods, 

 nich as blotters and soil. 



Laboratory tests are preferably made 

 between damp blotters placed in a 

 metal chamber heated by gas, the heat 

 being controlled by a thermo-regulator. 

 The blotters must be free from soluble 

 chemicals. Blue blotters will be found 

 less trying to the eye than white. The 

 germinating chamber may be of any 

 form which allows proper control of 

 the conditions of light, heat, air and 

 moisture. The standard chamber 

 adopted by the association of Ameri- 

 can Agricultural Colleges and Experi- 

 ment Stations was designed by the 

 writer, and serves equally well for 

 bacteriological purposes or experi- 

 ments in plant physiology as for seed 

 testing (see Fig. 2296). 

 It is made of 20-ounce corrugated copper, and is 2 feet 

 long, 18 inches deep, and 2 feet high, outside measure- 

 ments. The outside, except the bottom, is covered with 

 two layers of felt, each % inch thick. 



A water space is afforded by the double walls, which 

 extend on all sides except the front and are 2 in. apart. 

 Entrance; to this water jacket is obtained atrt,a (Fig. 

 22%), while the water can be drawn off at g. At c, c, on 

 the top, and at f, near the bottom of one end, are 1 inch 

 openings into the chamber. One of the upper openings 



SEEDA'.K 



1643 



\ . 



Una 



2295. 



Bottle similar to 

 that used in 

 U. S. Dept. 

 Aerie, for small 

 seeds. 



may be used for the insertion of a thermometer, if d,-- 

 snvd Owing, however, to the inline,,,-,. W |,j,.|, ,. 

 ternal atmosphere exerts ,, thermometer. . 

 tubes are partly exposed, provision has 1,,.,-n made for 

 holding two thermometers ; ;l |,,,ri/,,i,t : .l position, one 

 on the inside of each panel ,,f the door to the .-number 

 by means of hooks of stont copper wire < 1'i^. 22:1 7. 



Toe door is made in 2 panels, each con-i-tini: of 2 

 plates of thick glass set about % in. apart in a copper 

 trame, which is covered inside with felt. The in-nl- 

 margin of the door is provided with a projection 

 oo,4' C) which flts snugly into a felt-lined groove (Fii;. 

 JBW7, 6), extending around the front side of the cham- 

 ber. The door is 3 in. shorter than the front of the 

 chamber, the remaining space hein^ ,-losed with copper 

 and provided with a ventilator (Fig. L'2'.Hi, h), which per- 



2296. Standard seed-eerminatine chamber (front view, with 

 one door slide removed). 



Used by the United States Department of Agriculture 

 and American Experiment Stations, a. a, openings 

 into water jacket ; 6. thermo- regulator; c, c, openings 

 into chamber; d, gas entrance tube ; e , mirrobunsen 

 burner: f, gas exit; g, water exit; h, ventilator; , j, 

 door slides; k, pun to hold porous saucers, etc.; /, blot- 

 ter test; in , porous saucers with saud test. 



mits the exit of carbon dioxid, and can be closed tightly 

 with a slide. Perfect closing of the door is further ef- 

 fected by a copper slide extending along the front mar- 

 gin, which catches firmly at the top and bottom of the 

 chamber (Fig. 2297, d,d). This device, together with 

 the groove and its corresponding projection, are adapted 

 from the Rohrbeck bacteriological chamber. The out- 

 side door is furnished with a frame into which slide 

 two plates of galvanized iron painted dead black inside 

 and covered with felt (Fig. 2296, t, j). By this arrange- 

 ment the interior of the chamber may be kept dark or 

 exposed to light, or, if desired, one-half may be dark 

 and the rest light, the other conditions remaining the 

 same. By raising these slides the thermometers can be 

 read without opening the door. Glass plates of various 

 colors may be substituted for the slides, if the effects 

 of different rays of light on plant-growth are to be 

 studied. 



Seven movable shelves, placed 2M in. apart, are held 

 in place by copper ledges % inch wide. These shelves 

 are made of brass rods 1J-6 in. apart, and each one is 

 capable of holding up GO pounds wei-ht. The tempera- 

 ture is controlled by a low-temperature thermo-regulator 

 (Fig. 2296, 6). A very low and equable flame is secured 

 with a microbunsen burner ( Kiir. 22%. e). One of the 

 openings into the water jacket (Fiir. -"-".Mi, ) is 2 in. in 

 diameter to admit a Koux thermo-regulator, if a very 



