12  SMITHSONIAN    MISCELLANEOUS    COLLECTIONS  VOL.    96 
reach  the  seedlings,  the  first  internodes  were  very  much  longer  than 
the  coleoptiles.  These  differences  in  lengths  of  first  internode  and 
coleoptile  clearly  show  the  marked  effect  of  Hght.  Even  the  dark- 
control  plants  exposed  to  a  minute  amount  of  scattered  or  diffused 
light  showed  that  the  seedlings  are  extremely  sensitive  to  light.  It 
is  rather  remarkable  that  such  small  amounts  of  radiation  should 
completely  change  the  relative  length  of  first  internode  and  coleoptile. 
Table  3. — Data  Shoiving  Average  Length  {mm)  of  First  Internode,  Coleoptile, 
and  Total  Oat  Seedling  After  Four  Days'  Groiuth  in  Light  (Approximately 
13  to  7  ergs/cm^/sec.)  of  Mercury  Lamp  and  in  Darkness,  at  the  Indicated 
Maximum  and  Minimum  Temperature  (°  F.) 
[Average  Data  in  Boldface  Type] 
In  same  moisture  chamber 
Wave 
length 
Exposed 
A 
Dark  control 
Separate  chamber 
Dark  control 
A 
Temperature 
A 
Int. 
Col. 
Total 
Int. 
Col. 
Total 
Int.         Col. 
Total 
Max. 
Min. 
4047 
15 
27 
42 
22 
10 
32 
75 
74 
20 
45 
65 
45 
21 
66 
79 
76 
24 
23 
47 
48           7 
55 
79 
76 
25 
35 
60 
48 
15 
63 
73         II 
84 
78 
77 
21 
33 
54 
38 
15 
54 
61           9 
70 
4358 
26 
40 
66 
51 
16 
67 
66        II 
77 
79 
77 
25 
38 
63 
52 
16 
68 
66        II 
77 
78 
76 
25 
34 
59 
47 
13 
60 
60          8 
68 
78 
77 
25 
37 
63 
50 
15 
65 
65       10 
74 
5461 
20 
32 
52 
39 
15 
54 
63          8 
71 
77 
76 
14 
21 
'35 
33 
13 
46 
57          7 
64 
76 
76 
20 
28 
48 
38 
13 
51 
48           7 
55 
75 
75 
20 
39 
59 
43 
17 
60 
55         10 
65 
79 
78 
19 
30 
49 
38 
15 
53 
56          8 
64 
5780 
17 
49 
66 
45 
36 
81 
61         10 
71 
79 
78 
19 
47 
66 
47 
31 
78 
50         8 
58 
80 
79 
20 
46 
66 
45 
28 
73 
67        10 
77 
78 
78 
19 
47 
66 
46 
32 
77 
59          9 
69 
The  average  total  seedling  lengths  for  the  three  series  are  58,  62, 
and  69  mm,  corresponding  to  the  exposed,  "  diffused  "  control,  and 
totally  dark  control,  respectively.  Here  again  the  effect  of  light  is 
noticed.  The  total  length  is  greatest  in  complete  darkness,  less  in 
the  presence  of  minute  scattered  light,  and  least  in  the  illuminated 
series.  Although  the  total  length  is  not  greatly  changed  by  light,  as 
was  true  in  the  first  series  of  experiments,  yet  there  is  a  distinct 
indication  that  total  growth  is  less  and  that  the  activity  of  growth 
substance  or  regulators  is  slightly  decreased  even  by  very  weak  light. 
