Table 1.

Analysis of covariance for critical photoperiod with altitude-corrected latitude (ACL) from pooled 2-year samples as a covariate and year sampled (Yr) as the treatment, using type III sum of squares in the glm procedure of SAS (26)

Treatment	1972 vs. 1996		1988 vs. 1993
	F1,34	P	F1,10	P
ACL	975.24	<0.001	546.45	<0.001
Yr	4.17	0.049	3.41	0.095
ACL × Yr	7.85	0.008	7.35	0.022