1899] THE CEREAL RUST PROBLEM 341 



Fusarium lycopcrsici, Sacc, the fungus causing the tomato disease. 

 This discovery was announced in a footnote to Collenette's paper 

 quoted above. During further experiments with seed from diseased 

 tomatoes sent by Collenette, I was able to corroborate the presence of 

 slender hyphae in the testa of the seed, and furthermore obtained both 

 the Diplocladium and Fusarium stages of the fungus by placing sections 

 of the diseased seeds in a culture medium. 



The above experiment leaves no doubt as to the fact of seed pro- 

 duced by a diseased tomato fruit being able to perpetuate the disease, 

 due to the presence of latent mycelium — not mycoplasma — in the 

 testa of the seed. 



Experiments with Hollyhock seeds gave similar results. When 

 the carpels are attacked by the Hollyhock rust — Puccinia malvacearum, 

 Mont. — the testa of the seeds frequently contain mycelium, and such 

 seed when sown, if it germinates at all, gives origin to a large per- 

 centage of diseased seedlings, the teleutospores of the fungus appear- 

 ing on the hypocotyl and on the cotyledons in abundance. This 

 experiment is of considerable importance, as the fungus belongs to the 

 same genus as those producing rust on cereals. 



Ustilago vaillantii, Tul., a fungus infesting the anthers, and some- 

 times also the ovary, of Scilla bifolia, and other allied plants, has been 

 under constant observation for the past six years with the object of 

 ascertaining its complete life-history, which is intended for publication 

 in detail in the near future. The leading points in its history bearing 

 on the question at issue are as follows : — Quite young seedlings may 

 be infected by spores present in the soil. A perennial mycelium is 

 formed in the short stem at the base of the bulb ; from this hyber- 

 nating mycelium hyphae pass into the flower-stalk each season ; this 

 mycelium finally reaches the anthers and the ovary. The mycelium 

 is only present in the tissues at any given time for a length of about 

 2 mm. — in other words, as the mycelium creeps up the tissues of the 

 flower-stalk it deliquesces and disappears behind, the growing tips of 

 the mycelial strands only being at any one time evident, and when it 

 has passed into the anthers there is not a vestige of mycelium to be 

 found in the filaments of the anthers. All this takes place while the 

 flower is in the bud condition, and the whole inflorescence is vet 

 underground. When the fruit is attacked all the seeds are often 

 completely destroyed, their position being occupied by a powdery black 

 mass of fungus spores. In other instances only some of the seeds are 

 destroyed, others present in the same fruit remaining apparently 

 healthy ; but on microscopic examination of such seeds slender 

 mycelium can often be detected in the testa. Apparently healthy 

 seeds obtained from a fruit having some of its seeds destroyed by the 

 fungus, when sown in sterilised soil, and freed from adhering fungus 

 spores by proper methods, always yield a large percentage of diseased 

 seedlings, the mycelium soon being quite conspicuous in the delicate 



23 NAT. SC. VOL. XV. NO. 93. 



