2 7 2 RESEARCHES ON FUNGI 



surface of the epidermis where they can be very clearly seen when 

 the coleophyllum has been removed and is examined under the 

 microscope. Now, as the results of our three series of experiments 

 clearly indicate, these germ-tubes must sometimes penetrate into 

 the seedlings and cause infection there. Nevertheless, in spite of 

 many observations on our part made both with and without the use 

 of Giemsa stain, in no instance did we succeed in actually perceiving 

 a germ-tube penetrating through the epidermis or growing within 

 the epidermis or other tissues of the host-plant. So far as we are 

 concerned, therefore, the exact place and mode of entry of the germ- 

 tubes into wheat seedlings still remain to be elucidated. 



The Swelling of Bunted Wheat Grains in Water. — Prevost 1 

 states that bunt-balls placed on the surface of water swell up con- 

 siderably and that, within a few minutes, the spores in some of them 

 are forced out en masse through some crack in the pericarp, with 

 the result that they sink down through the water in the containing 

 vessel like a cloud of descending smoke. 



Prevost's experiments were repeated and confirmed (Fig. 134). It 

 was found that the spores are forced out only from those bunt-balls 

 which already have injured pericarps, and that bunt-balls with un- 

 broken pericarps, although they absorb water freely so that they swell 

 up and become turgid, do not liberate any of their chlamydospores. 



Dry bunt-balls, when put into water, rise to the surface and 

 float there for an indefinite time. In the course of a few hours 

 the floating balls absorb much water. If, when absorption is com- 

 plete, the balls are pressed beneath the surface of the water, they 

 at once sink to the bottom. 



Some intact floating balls were kept in a beaker in the 

 laboratory and, after 6-8 weeks, masses of chlamydospores 

 were observed to be exuding from them at the water-line. 

 Their pericarps had been weakened and finally ruptured by species 

 of Alternaria, Cladosporium, and Mucor, which had grown upon 

 them saprophytically. According to Woolman and Humphrey, 2 



1 B. Prevost, Memoire sur la Cause Immediate de la Carie ou Charbon des Bles, 



Paris, 1807, p. 3. 



2 H. M. Woolman and H. B. Humphrey, Studies in the Physiology and Control 

 of Bunt or Stinking Smut of Wheat, U.S. Department of Agriculture, Bull. No. 

 1239, 1924, pp. 6-7. 



