lOO Journal of Agricultural Research voI.xix.No.s 



it does not develop properly but becomes stunted and functionally 

 inadequate. 



The subsequent fate of an infected plant varies with conditions. In 

 the rainy season it almost invariably succumbs rapidly to secondary in- 

 fections by species of Pythium, Helminthosporium, or Fusarium. In the 

 dry season, however, although it usually turns brown, withers, and soon 

 dies, such a plant may struggle along to the tasseling state and may even 

 produce a stunted ear with occasionally a few grains. 



When the disease appears later in the development of the corn plant 

 the symptoms are as follows : The first leaf to show any signs of the disease, 

 which may be the fourth or fifth or even up to the eighth, will have at the 

 base pale stripes similar to, but more extensive and broader than, those 

 described for plants which show the disease early (Pi. B). All subse- 

 quent leaves show a somewhat similar striping but in a progressively 

 more marked degree, the markings on each successive leaf being more 

 extensive than those on its predecessor and running nearer the tip, while 

 the last leaves are striped throughout their entire length. 



The shape of the stripes varies greatly. On the lower leaves they are 

 usually merged at the base into a solid yellowish white area from which 

 irregular elongations run up into the normal green towards the tip of the 

 leaf (PI. B). On the middle leaves the solid yellowish w^hite area at the 

 base is somewhat smaller in extent, but the prolongations from it run 

 more nearly to the tip, while on the upper leaves these discolored stripes 

 extend from the base to the tip of the leaf but are more broken and irregu- 

 lar and even merge laterally and anastomose so that a marbled or mottled 

 appearance is given to the otherwise green leaf. 



The shape and size of these leaves, however, is very little altered, and 

 they usually have the breadth and flexibility which characterize leaves 

 of the normal plant. At times, however, the midribs become brittle 

 from the invasion of the fungus mycelium, break where they join the 

 sheath, and hang straight down along the stem (PI. 17). The growth 

 and structure of the stem are often normal, and the root system is strong 

 and well developed. It is in the reproductive structures of these later- 

 infested plants that the injurious effect of the disease is shown especially. 

 The tassel, although usually appearing at the normal time and often 

 seemingly unharmed structurally, may show decreased production of 

 pollen and frequently is extremely malformed (Pi. 17, A). The ear also 

 is even more seriously affected. Even a mediocre ear is a very rare 

 occurrence (in i out of 150 diseased plants), while customarily the ear 

 is more or less completely sterile and malformed (PI. 20). 



This malformation of the reproductive structures is of frequent and 

 regular occurrence in maize infected by the Philippine downy mildew. 

 In plants attacked at all ages by the disease there is induced a great 

 variety of the most remarkable malformations and monstrosities of the 

 ear and tassel. These show a wide range of the fasciations, phyllodies. 



