40 



PROTECTION OF PLANTS, 1921-22 



but so far as is known no reference has been made anywhere to attack of 

 chemical wood-pulps by molds. The purpose of this short article is to state 

 that material has been submitted to the Forest Products Laboratories , of 

 Canada showing a molded condition in sulphate and soda pulps and sulphite 

 both bleached and unbleached. 



The first appearance of moldiness occurs as small discoloured spots of 

 which a number are often found in a single sheet. The discoloration is usually 

 dark grey, black or brown but it may also be greenish, yellowish or a deep pink. 

 At the outset the actual harm done to the pulp may be very slight, consisting 



Fig. 1. — ^Fibres taken from mold spot in Sulphite pulp, x 300 



principally in a discoloration limited to small areas. If the action is not 

 checked the discoloration spreads until the pulp finally becomes worthless. 

 The early discoloration may lower the price of the pulp out of all proportion 

 to the actual damage caused as the small amount of material containing the 

 coloured matter is so broken up in the beater that the colour of the paper 

 made from it is not appreciably changed. 



The accompan3dng photomicrographs show conditions found in the 

 different kinds of pulp studied. 



