IOWA ACADEMY OF SCIENCE 
47 
ephacelial stage of ergot? These flies in favorable season like 1907 in Iowa, 
produce a wide-spread infection. The cabbage butterfly is largely responsible 
for conveying not only the cabbage rot {Pseudomonas campestris) but a bene- 
ficial bacterial disease destructive to the larvae of the same insect. Insects are 
also largely responsible for carrying the rust of the red cedar ( G^mnospomn- 
gium macropus) to the apple tree. The cedar apple fugus furnished a very 
attractive food for them. Bees, the hctive pollinators of the apple, also carry 
the bacteria of apple blight, which is found according to Waite in the nectar 
of the blossoms of the apple. Aside from this conveyance, flies feeding on the 
exudate on the stems affected by pear blight also convey the disease. Insects 
feeding on rust spores convey the same to neighboring plants. 
Plies and other insects aid in scattering spores of the spot disease of the 
cherry. These spores cling together in a sticky tendril-like mass; this material 
is said to have a sweet taste. Water also aids in dissemination of spores of 
cherry spot disease. 
The common Stinkhorn (Phallus impudicus) which frequently causes trouble 
in orchards and gardens because of the bad odor, is chiefly disseminated by 
flies that feed on the spores. 
Ergot (Glaviceps purpurea) is commonly carried from cultivated to wild 
rye and other grasses, by common flies which feed on the honey dew stage 
(Sphacelia) of the fungus. 
Gardiner^® describes how contrivances for assisting plants to maintain them- 
selves in the struggle for existence are found in fungi and algse; as in the 
case of Queensland fungus, Clathrus, which has orange red color, strong 
smelling spores, and is enveloped in a sweet mucilage, thus using the same 
advertisements, color, scent, and sweetness, employed in higher plants. The 
mildew of alder has hooked fruits, which are possibly carried about by tiny 
Acari. Spores are shot out with some force from the mycelial filaments of 
the fungus that attacks flies. The spores of Sclerotinia Vaecinii have an al- 
mond smell, and are gathered by bees with pollen, and conveyed from one 
plant to another. 
The influence of insects in carrying diseases is well illustrated in the com- 
mon lima bean mildew (Phytophthora phaseoli). Dr. Sturgis®® calls attention 
to the structure of the flower of the lima bean and its adaptation to cros^ 
pollination. The insects (bees) that pollinate the flowers are largely respon- 
sible for conveying the disease. Dr. Sturgis says: 
“Further investigation confirmed this view. I have called attention to the 
enclosed and protected position occupied by the pistil; this obtains until the 
flower is visited by an insect of considerable size, generally a honeybee. The 
projecting wing-petals offer a convenient landing place, and, as the bee alights 
on them, his weight deflects both wings and keel, the style is protruded from 
the keel, the bee’s abdomen brushes over it, and in his efforts to reach the 
bottom of the flower the petals are forced apart, the base of the ovary exposed 
and the bee’s head comes in contact with it. Thus cross-fertilization is secured, 
but if the bee has, by chance, touched a mildewed pod with either head or 
abdomen, fungous infection no less surely occurs. It will be noted that the 
only portions of the pistil touched by the bee are the base of the ovary and 
-®Miss Estelle D. Fogel Rep. la. State Hort. Soc. ^1:105. 1907. 
2®Gardiner Abstr. in Nature. 41:91. 
soRot. Gaz. 25:192. 
