DETAILED ACCOUNT OF SPECIFIC PLANT DISEASES 525 



fissures. The club-shaped asci bear eight acicular ascospores between 

 which are found paraphyses with hooked tips. These ascospores 

 measure 65 to 8o> by 1.5 to 3/i and are ejected forcibly from the ascus. 

 As the disease is not a serious one, usually no remedial measures are 

 necessary. If the owner of maple shade trees wishes to keep it in 

 check, he should burn the dry maple leaves which litter the ground 

 about his place. 



Melons, Squashes, Watermelons {Cucurbita spp.) 



Anthracnose {Collelotrichum lagenarium (Pass.), Ell. & Hals. — ^As 

 an illustration of a disease-producing fungus included among the Fungi 

 Imperfecti, we may describe briefly the anthracnose of cucumbers, 

 squashes, watermelons, CoUetotrichum lagenarium, which attacks 

 both leaves and fruits. The leaves are found with brown spots which 

 cause their early maturity. If the fungus attacks the fruits, it produces 

 sunken water-soaked spots in which the acervuli appear. The acervuli 

 produce numerous conidiospores sticking together to form viscid 

 masses of a pink color. During moist weather, the hyphae may grow 

 out, superficially covering the fruit with a mold-like growth. The 

 fungus eventually causes a complete decay of the fruit. The disease 

 has been prevalent in Nebraska and New Jersey. If the disease 

 appears in greenhouse culture, it is well to sulphur the greenhouses 

 thoroughly when they are empty, and to clean and whitewash all the 

 walls and woodwork to destroy any funguses present. Spraying with 

 Bordeaux mixture (3-6-50) should begin when the vines begin to trail 

 over the ground. Subsequent sprayings should be made every ten 

 days, if the weather is dry. 



Wilt {Bacillus tracheiphilus , E. F. Sm.). — This serious disease of 

 cucurbitaceous plants was first reported by Erwin Smith about 1893. 

 It was first known in the northeastern states, but it is now common in 

 the middle west and Rocky Mountain regions. Although pumpkins 

 and squashes may be attacked by wilt, yet cucumbers and melons are 

 most susceptible. This microorganism, which is a rod-shaped bacillus 

 two or three times as long as broad, is actively motile by wavy cilia 

 only when young. It measures 1.2 to2.5/i by 0.5 to 0.7/i. It causes a 

 progressive wilting of the host which it attacks. Whether the whole 

 plant dies depends upon the point of infection, which is usually ac- 



