VARIATION IN ARUM MACU LATUM 



By C. T. Prime 



A study of variation in Arum maculatum L. was made as part of an investigation 

 into the general biology of the British species, and the following paper gives a short 

 account of the results. 



1. Leaf variation 



A. maculatum is slow to germinate; in the first six months the hypocotyl develops 

 a small tuber which by the autumn following (one year after sowing) has developed three 

 or four roots with a small shoot. The first leaf appears above ground in the following 

 spring. This leaf is oval and only after three or four years is the characteristic sagittate 

 shape developed. At maturity the plant usually bears three leaves though the number 

 varies between two and four or even five. The most characteristic shape is shown by 

 the second and third leaves, the first leaf being generally smaller, and borne on a shorter 

 petiole (Table 1). 



Table 1 

 Leaf length in Arum maculatum 



Length of first leaf 8-47 cm. ± -12 (a = 1-32) 



Length of second leaf 10-69 cm. ± -12 (a = 1-48) 

 Length of third leaf 11-79 cm. ± -12 (a = 2-20) 



The third leaf may vary in length from 5-19 cm. and from 4-14 cm. in width. Obser- 

 vation and measurement show that any particular leaf form tends to be retained year by 

 year (Table 2). 



Table 2 



The correlation between leaf dimension in successive years in Arum maculatum 



Petiole length in 1943 and 1944 -58 (P.E. - -09) 

 Leaf length in 1943 and 1944 -48 (P.E. = -09) 

 Leaf width in 1943 and 1944 -31 (P.E. -06) 



The distribution of the spotted and unspotted leaf forms (var. immaculatum) has 

 been investigated by Pethybridge (1903) who gives the following results. 



Sussex : 99% unspotted 



Hereford : 5:1 unspotted to spotted 



Lincoln : 92% unspotted 



Northumberland : 90% unspotted 



Ireland : 500 : 1 unspotted to spotted 



It is not said how these figures were obtained, whether they were visual impressions or 

 otherwise. Bromfield (1856) also says the unspotted form is commoner in the North of 

 England. 



A more thorough investigation was undertaken with the assistance of other observers, 



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