Manchester Memoirs, Vol. Ivii. (19 13), No. 11. 13 



given by these investigators do not, however, extend to 

 the relations of the haustoria to the cytoplasm and 

 nucleus of the cells. From many of the figures it is not 

 even clear whether the haustoria are lying in the proto- 

 plasm of the cell or are hanging into the vacuole. 



This vagueness is not by any means surprising in 

 view of the difficulties I have encountered in dealing with 

 fixed material of these pathological cells. It soon became 

 evident that a fuller understanding of the delicate relation- 

 ships of the haustoria to the cells could only be obtained 

 by checking the observations on fixed material by a 

 study of cells in the fresh or living condition. Without 

 this comparison it was difficult to say how far the changes 

 in the cells were due to the action of the fungus or merely 

 to the difficult}- of fixing the abnormal cells. 



Haustoria are found in practically every cell of the 

 tissues, the intercellular spaces of which are occupied by 

 the fungus. They vary somewhat in form according to 

 the character of the cell invaded. In the cells of the 

 collenchjma and assimilating tissue they are generally 

 forked, and each branch grows towards the nucleus. In 

 the cells of the cortical parenchyma the haustoria are 

 often larger, but when first entering appear as short 

 straight or forked hyphse, connected with the hypha out- 

 side by a fine neck {PL /., Figs. 5 and 6). They grow 

 toward the nucleus, and often flatten the tip, or tips, of 

 their branches against the nuclear membrane {PI. /., 

 P^S- ?)■ ^" t^iG cells of the starch sheath the haustoria 

 are generally much more branched, and the branches enter 

 into close contact with the nucleus {PI. /., Figs. 9, 10 and 

 11). The haustoria in the elongated cells of the phloem 

 parenchyma enter by a narrow neck and the two branches 

 diverge, growing in opposite directions a limited distance 

 along the cell {PL I., Figs. 12 and 13). The nucleus of 



