191 !• CoLGAN. — Leaf'blotchings in Arum maculatum. 213 



of an inch long. Six of the 11 plants bore leaves absolutely 

 immaculate and unpittcd. 



This division of the seedlings into spotted and unspotted 

 forms at once suggested the action of Mendelian factors, and 

 having discussed the problem with Mr. G. P. Farran, he 

 proposed the following solution, which it seems to me is one 

 that further experiment may very likely prove to be true. 

 On the assumption that we have here to do with Mendelian 

 characters, he regards the 11 seedlings as the outcome of 

 a cross between a pure-bred immaculate-leaved plant and 

 a hybrid spotted and pitted-leaved plant. In accordance 

 with Mendel's laws such a cross should produce equal numbers 

 of the two parent forms, and this result has occurred in the 

 case of the Newcastle fruiting Arum as closely as is possible 

 in dealing with an odd number of seeds. On the same 

 assumption as to the hybrid nature of the plants and the 

 Mendelian character of their spots and pittings, a cross 

 between two of these hybrids should have given rise to 3 

 spotted seedhngs for every one unspotted, or say 8 spotted 

 to 3 unspotted out of the 11 seeds sown. And such a cross 

 might very easily have taken place since two of the assumedly 

 hybrid Newcastle plants flowered side by side in my garden 

 in May, 1909. The actual proportion of spotted to unspotted 

 seedlings produced may be taken, then, as showing that no 

 such crossing of hybrids did in fact take place, but that the 

 fruiting plant which bore the 11 seeds was fertilized by the 

 pollen of an ordinary unspotted Arum. The only Arums 

 grown in my garden were the spotted and pitted Newcastle 

 plants, so that the fertilizing pollen must have been insect- 

 borne from outside. The ordinary unspotted plant grows 

 certainly within one-third of a mile of my garden, and may 

 perhaps grow much closer at hand in copses which I have 

 not examined. The problem is one that invites further 

 experiment with artificial fertilization. 



Some time after I had completed the observations just 

 recorded, it occurred to me to look into the literature of the 

 subject, and by the kind assistance of Dr. Pethybridge and 

 Prof. Johnson, I was enabled to study at hrst-hand two 

 important papers on the development of Arum maculatum 

 to which they drew my attention. The first was a paper by 



