7i8 FUNGI 



disease in the crop. It is found, however, that the germ-tube of 

 the conidia penetrates into extremely young plants, and that this 

 infection takes place in the soil. In the ordinary course of things 

 the grains and the ' smut ' spores adhering to them from the previ- 

 ous season are sown together in the spring. Both the grain and 

 the chlamydospores germinate about the same time, and the germ- 

 tubes of the conidia produced from the latter, penetrate into the 

 first leaf-sheath of the oat plants while these are but a few hours old. 



Once inside a young plant, the germ-tube grows and branches, 

 extending itself from cell to cell until it reaches the growing point, 

 and as the latter shoots upward the mycelium of the fungus 

 steadily advances with it : at the same time there is little or no 

 external evidence of the presence of the parasite within the tissues 

 of the infected plant. The older hyphae in the lower parts of the 

 plants soon die away, their protoplasm being continuously trans- 

 ferred to the advancing hyphae so that at any particular moment 

 the mycelium of the fungus is only discoverable in the youngest 

 upper portions of the oat stem. When the ear is developing the 

 fungus enters the ovary of the flower and feeds upon the plastic 

 materials which would ordinarily be stored in the endosperm 

 tissue for the benefit of the embryo. In consequence of the 

 increased nutrition the mycelium develops extensively, permeates 

 all parts of the flower and destroys almost each hypha, finally com- 

 pletely dividing into a number of separate chlamydospores which 

 burst through the remaining epidermal tissue of the glumes and 

 grain. Brefeld's recent researches have shown that the oat plant 

 may also be infected through the open flowers. The 'smut' spores 

 blow about at the time of flowering, germinate on the stigmas, and 

 penetrate into the ovary below. After gaining an entrance in 

 this way, the fungus remains dormant in the grain until the latter 

 is sown in spring, when it invades the young awakening embryo. 



' Smuts ' of Wheat, Barley and Rye. — Formerly all ' smut - 

 fungi on these cereals and on oats were considered as one species. 

 Small morphological differences are, however, observable between 

 the ' smuts ' from the different cereals, and it is also found impos- 



