60 FLORA OF MICHIGAN. 



of things seems to prevail in reference to parasitic fungi. For example, 

 fungi infesting cultivated grapes sometimes sweep down with great severity 

 in many sections where vineyards are large or numerous, while a 

 few vines in isolated neighborhoods may often escape uninjured. So it is 

 with rust, smut and bunt on wheat, smut on corn, lettuce mold, rust on 

 onions, and black knot on cherries and plums. 



Recently the life history of many fungi injurious to cultivated plants, 

 including some experiments with materials to check their progress, has 

 received considerable attention in this country. 



As we have insects which by preying on other injurious insects are ben- 

 eficial to the progress of agriculture and horticulture, so we have a goodly 

 number of fungi which prey on our weeds and tend more or less to keep 

 them in check. Recently there have been a few successful efforts made 

 in introducing the proper insects to prey on injurious insects. In time 

 very likely there may be introduced certain parasitic fungi which shall 

 aid in the extermination of weeds. 



At the Agricultural College, Shepherd's Purse in many places has been 

 nearly all destroyed by a parasitic fungus, Cystopus candidus. Lev. Com- 

 mon purslane has been much checked by Cystopus Portulacce, DeBy, and 

 in a few places the common elder by JEcidium sambuci, Sch. For some 

 years past, large patches of the common milkweed have disappeared grad- 

 ually, one after another, through the agency of some disease possibly a 

 microbe. Three species of milkweed are similarly affected. One attempt, 

 as yet unsuccessful, has been made to disseminate this milkweed disease 

 to neighborhoods where the plants are abundant and thrifty. 



In these parasitic fungi we see an important factor which helps control 

 the geographical distribution of plants, and may there not be something 

 here to help explain why certain foreign species for a time are often so 

 vigorous in a new country? Isolation is favorable to thrift, while large 

 masses are opposed to long continued escape from the ravages of insects 

 or parasitic fungi. 



It was a part of our plan to prepare a list of parasitic fungi, especially 

 so far as seen at the Agricultural College, but we have not yet been able 

 to make it complete enough to satisfy us. 



FLOWERING PARASITES AND SAPROPHYTES DESTITUTE OF GREEN LEAVES. 



There are a few native flowering plants which are destitute of green 

 throughout their growth and development. They subsist entirely on 

 decaying animal or vegetable matter, or to some extent on matter as it is 

 assimilated by growing plants, or they may live entirely on what they can 

 take from such plants. 



The list is a short one and includes: 



Aphyllon fasiculatum, Gray. Cancer-root. 



* uniflortim, Gray. Cancer-root. 

 Conopholis Americana, Wallroth. Squaw-root. 

 Cuscuta chlorocarpa, Engelm. Dodder. 



" Gronovii, Willd. Dodder. 



" tenuiflora, Engelm. Dodder. 

 Epiphegus Virginiana, Bart. Beech-drops. 

 Monotropa Hypopitys, L. Pine-sap. False Beech-drops. r 



uniflora, L. Indian Pipe. Corpse-Plant. 

 Pterospora Andromedea, Nutt. Pine-drops. 



