State Museum of Natural History. 29 



exclusion from the full rays of the sun, it is quite probable that it 

 never attacks healthy and vigorous leaves, but only those already weak 

 and languishing. In this case it'would be but slightly different in its 

 habitat from those species that live on dead vegetable matter, and it 

 could only be said to hasten the death of the leaf by a few days or 

 weeks and therefore should not be regarded as a very noxious fungus. 

 It is not unusual to find another fungus, a species of Macrosporium, 

 associated with it and growing on parts of the leaf that have been dead 

 for some time. This fungus is easily distinguished from the other by 

 its spores which are shorter and comparatively thicker and divided 

 into cells by short, longitudinal as well as transverse partitions. 



Puccinia Maydis, Potsch. Indian corn Brand. (Plate 3, figs. 7-11.) 

 Frequently in the latter part of the season the corn leaves are affected 

 by a fungus called the Indian corn Brand. Small pustules or tuber- 

 cles, technically called sori, appear on one or both sides of the leaf. 

 Sometimes they are accompanied by a discolored spot, but often there 

 is scarcely any discoloration. The pustules may be few and scattered 

 or numerous and more or less crowded, or even confluent, in which 

 case they form lines or irregular patches. At first these pustules are 

 covered by the thin epidermis of the leaf, but at length this is ruptured, 

 and then the fungus beneath is revealed. Some of the pustules, 

 especially at the time of the earliest appearance of the fungus, are 

 filled with rusty-red globular spores about one one-thousandth of an inch 

 in diameter. This is the Uredo-form or early state of the fungus, for 

 some fungi have different states or forms of development, just as in- 

 sects do. Other pustules, and a little later in the season all the pus- 

 tules, contain the true Puccinia or brand-spores. These are nearly or 

 quite black, and before the covering epidermis is ruptured the pustule- 

 containing them have a peculiar livid or lead color. The covering of 

 the pustules usually ruptures in a longitudinal direction, that is, lengths 

 wise of the leaf, either through the middle or near one side of the 

 pustule. In the latter case the broad fragment of the epidermis forms 

 a kind of flap that remains and partly covers the cluster of spores. 

 Each pustule contains many spores closely packed together in an up- 

 right position. When highly magnified they are found to be two or 

 three times as long as broad, and to have a single transverse partition 

 which divides each spore into two cells nearly equal in size. A pale 

 pedicel of variable length is also attached to the base of each spore. The 

 spores themselves vary in length from sixteen to twenty ten-thousandths 

 of an inch, exclusive of the pedicel. They are very persistent and may 

 still be found in the pustules of old leaves in the Spring of the next 

 year. Thus it appears to be the office of these brand-spores to carry 

 the fungus through the Winter. 



The species of Puccinia are very numerous and all inhabit living 

 plants. Most of them, as in the present species, are known to have 

 two or more forms of development. They do 'more or less injury to 

 their supporting plants, according to the greater or less abundance of 

 the parasite, though they do not usually kill the plant they attack. 

 By interfering with the office of the leaves and abstracting therefrom 

 nourishment thatshould go tothesupport of the plant, they must nec- 

 essarily impair its strength and vigor. Experiments are greatly needed 



