A DISEASE OF CL'PRESSUS PLANTS. 617 



nor have the spores been observed to exude from them in a 

 visible mass except under abnormal artificial conditions, when 

 they ooze out in tiny white drops, not in tendrils. 



The spores differ slightly in shape and in size. 



In artificial cultures, pycnidia form abundantly in every 

 i7iedium used, not only " sparingly on prune and corn-meal agars." 



With regard to the fungus on the former, no dull orange-red 

 colouration was observed. 



The natural hosts are different. The Phoma in (juestion 

 occurring on the three species of Cupressus — inacrocarpa, 

 ariconica, lorulosa — and the other on red cedars { Jiiulpcnis sjip.). 



Summary. 



1. As a result of inoculation and cultural experiments in 

 191 5 a Phoma (identity rather doubtful) was established as the 

 cause of a serious disease in young plants of Cupressus sp. This 

 has recently been identified with a Phoma on red cedars, described 

 by Hahn. Hartley, and Pierce. 



2. Symptoms are described as characterized by a discolora- 

 tion followed by withering and death, the dead leaves and twigs 

 showing the presence of small black dots, which are the fruiting 

 bodies of the fungus. 



3. The 'fungus is described as it occurs naturally, and in 

 artificial cultures. 



4. Inoculation experiments resulted in injured plants becom- 

 incr readily infected in a few days, and uninjured ones only with 

 difficulty in a few weeks. Moisture was proved to be essential 

 for the development of the disease. 



5. Control measures are given. Spraying with Bordeaux 

 Mixture is recommended on account of the spores being highlv 

 sensitive to copper sulphate. 



DESCRIPTION OF PLATES. 



Plate 18. — Young plants in early stage of infection by Phoma sp. 



Plate 19 a. — Older plants showing infection. 



Plate 19 b. — Dead twig of Cupressus macroearpa, showing the presence 



of Phoma pycnidia. 

 Plate 20 a. — Pycnidia formed in artificial culture. 

 Plate 20 h (i) . — iSpores before germination. 

 (ii). — Spores 24 hours after, 

 (m). — Spores 48 hours after. 

 Plate 21 a. — Tranverse section through diseased stem of C. }uacrocarpa, 



showing pycnidia and mycelial threads invading the 



broken-down cortical tissues. 

 Plate 21 b. — The same as Plate 21 a. through a leaf. 



N.B. — (/) and (n') of Plate 20 /» were drawn with camera lucida; all 

 other drawings were made with a Leitz projection apparatus. The 

 paintings were done by Miss K. Lansdell. 



Botanical Laboratories, 



Union Department of .\(;ri(:ulture, 

 Pretoria. 



