2IO The Irish Nalnralist. December 



ON THE INHERITANCE OF PITTED 



LEAF-BLOTCHINGS IN ARUM MACULATUM 



AND ON FLORAL VARIATIONS IN THE SPECIES. 



HY NATHANIEL COLGAN, M.H.I. A. 



Some eight years ago, in the March issue of this journal 

 for 1903, I drew attention to a pecuhar form of Arum 

 maculatmn occurring in Co. Dubhn, a form in which the 

 purple-brown maculations of the leaf were indented or 

 pitted on the lower surface so as to produce what were called 

 pseudo-blisters or protuberances on the upper surface. 

 This paper gave rise to an interesting discussion on the 

 whole subject of leaf-blotching in this species, and on the 

 distribution of the maculate -leaved variety in the British 

 Isles and on the Continent. In the course of this discussion 

 it appeared that the pseudo-blistering had been observed, 

 though rarely, in other stations, and that the pittings were 

 found to occur in some cases on the front or upper surface 

 of the leaf so as to cause answering protuberances to appear 

 on the back. Dr. Pethybridge (/r. Kat. xii., p. 149), ob- 

 served such indentings of the upper surface, as also did Mr. 

 R. A. Phillips {torn, cit., p. 205), and later {Flora\ Co. Dublin, 

 1904, p. 206) I recorded the hnding of a similar form by 

 Miss C. G. O'Brien near Foynes, Co. Limerick, and by 

 myself at Newcastle, Co. Dublin, in 1904. 



In the present paper it is proposed to give some notes on 

 the behaviour of several plants with blotched and pitted 

 leaves removed from the Newcastle station, and grown in 

 my garden for a period of 7 years, 1904 to 191 1. 



The first shoots from these transplanted tubers appeared 

 over ground usually in the first week in February of each 

 year, and on their first appearance the dark blotches showed 

 clearly on the outer surface or back of the closely furled 

 leaves. Even in this early stage, the nascent protuberances 

 could be traced in the region of the blotches. As the leaves 

 unfurled, the indentations or depressions on the upper 

 surface were e.xposed to view, and answering blister-like 

 elevations stood out prominently on the back (see Ir. Nat., 

 xvi., 177). The leaves, in fact, for seven successive years 



