302 TRANSACTIONS OF THE [Sess. lxxix. 



The irritation caused by P. obconica, Hance, comes from 

 a yellow substance, out of which monoclinic crystals 

 separate, which issues from the hairs which cover it in 

 all its parts. Anyone touching the plant receives a 

 deposit of this upon the skin, and by anyone so infected, 

 if one may so say, the infection may be conveyed to 

 others by touch ; that is to say, the ailment is contagious 

 only. There is no question of an exhalation or of a 

 microbe conveyed through the air. The infective sub- 

 stance is soluble in alcohol, chloroform, turpentine, benzole, 

 and this gives suggestion of protection — apart from 

 exclusion of the plant from cultivation — to those who are 

 susceptible. Washing the parts that have touched the 

 primula immediately after tending will dissolve the hurt- 

 ful secretion and remove it. Once the itching has begun, 

 ordinary palliatives in skin irritation— zinc ointment with 

 boracic acid, for example — must be used. Here in Edin- 

 burgh, whether on account of the pachydermy of its people 

 or because the secretion is less virulent than it is elsewhere, 

 cases of dermatitis caused by the plant are few. No case 

 has been recorded from the Royal Botanic Garden, where 

 the plant has been cultivated since its introduction. Pro- 

 bably the number of individuals susceptible is everywhere 

 small, but the irritation in those attacked may be severe, 

 and the brand of popular prejudice has given the plant a 

 bad name which sticks to it. 



It is a misfortune for horticulture that a plant so 

 desirable for winter decoration of our greenhouses should 

 have attached to it this curb upon popularity ; the more 

 gratifying, therefore, is it that we have now the prospect 

 of an obconica race free from the offending habit of 

 P. obconica, Hance, itself. P. obconica, Hance, as we 

 know it from Ichang, is apparently the eastmost extension 

 of a type which in varying degrees of development extends 

 into Manipur and Sikkim, where it becomes — shall I say 

 — what is known as P. Listeri, King. Over the area of 

 distribution variations occur, and amongst them is that 

 in the direction of suppression of the infecting hairs, whilst 

 the plant retains its qualities of growth-form and flower 

 which have given the Ichang plant its horticultural value. 

 Such an innocuous form is amongst the recent accessions 



