224 TEXT-BOOK OF FUNGI 



leaves of the potato plant. Furthermore these are not 

 resting-spores, but germinate the moment they are mature, 

 and perish within a very short period of time unless they 

 happen to be located on the leaf of a suitable host-plant. 

 It is thus impossible for the European outbreak of potato 

 disease to have originated from spores. 



The disease must have come from the New World under 

 the form of hybernating mycelium in the tuber, and by the 

 same means it has unknowingly been sent from Europe to 

 various other parts of the world. 



At the present day Phytophthora has spread from the 

 potato to some allied European wild plants, a fact to be 

 borne in mind in connection with the possible means by 

 which a crop may become infected. 



As regards bulbs, Chionodoxa ludliae^ a beautiful early 

 spring-flowering bulbous plant, came to us from Asia Minor. 

 Some time after its introduction a variety of this plant, 

 described as differing in the possession of a * black eye,' 

 was imported. The * black eye ; proved to be due to the 

 presence of a smut fungus (Ustilago) developed in the 

 anthers. Further investigation showed that a perennial 

 mycelium of this fungus was present in the * cushion ' or 

 flattened stem from which the bulb-scales spring. This 

 mycelium grows up inside the flower stem, and produces 

 its spores in the anthers. The mycelium also passes from 

 the parent bulb into the young bulbs to which it gives 

 origin. Hence every bulb is infected, and in the majority 

 of instances bears smutted anthers, but not always. 

 Smutted plants have been under observation for the past 

 ten years at Kew, and although in the majority of instances 

 the anthers have been smutted, every now and again 

 flowers free from smut have appeared, although examina- 



