6l4 A DISEASE OF CUPRESSUS PLANTS. 



described, which, except for a few points which will be noted 

 later, agrees so well with the Phoma on Cupressus sp. that one is 

 forced to admit that they must be identical. This discovery has, 

 of course, rather upset the author's calculations, but seeing that 

 the investigations have been carried on quite independently and 

 on rather different lines, it is still thought worth while to publish 

 the results, if only to make a record of the points of difference, 

 and the natural occurrence of the fungus on a new host. 



Symptoms of the Disease. 



Up to the present, the disease has been known to occur only 

 in those parts of the country where summer rains prevail, and 

 only in very wet seasons, pointing to moisture as an important 

 factor in its development. It is primarily a disease of nursery stock. 

 Plants up to four years old may be attacked, but it is seedling 

 plants that are most susceptible, plants in seedling and trans- 

 plant beds dying off in hundreds. In such cases the symptoms 

 are particularly characteristic. Infection may start anywhere on 

 the plant — at the base, in the middle, or at the top — but is always 

 indicated by the leaves and stems becoming discoloured, assum- 

 ingr a water-logged appearance, withering and finally dying. 

 When the stem tissues are badly attacked, the plant bends over at 

 that part {PI. i8), the disease spreads rapidly, and young plants 

 succumb to it in a very short while. Older plants {PI. 19, a) are 

 liable to attack in exceptionally wet seasons, but are much more 

 resistant, with the result that they often recover, though they are 

 much deformed in shape. Small black dots — the pycnidia of the 

 Phoma — are present on dead leaves and young stems {PI. 19, b). 

 Under abnormally wet artificial conditions, but not under natural 

 ones, spores are seen to exude from these in the form of small 

 white drops, not in tendrils as described for the fungus on red 

 cedars. 



Transverse sections through diseased tissues show not only 

 Phoma pycnidia, but a very much deformed outline, and tissues 

 broken down and invaded by threads of a hyaline mycelium — in 

 the leaves, the palisade and spongy tissues, and in the stem the 

 cortical tissues {PI. 21, a and h). 



Description of the Fungus. 



The pycnidia are scattered and do not form spots. They 

 develop superficially just below the cuticle, and appear to be 

 erumpent only at maturity. In shape they may be globose, but 

 are usually lenticular. On specimens of C. Macrocarpa they were 

 found to be unilocular, but on C. arizonica and torulosa they were 

 occasionally indistinctly plurilocular. They vary in size, measur- 

 ing 122-290 /A wide X 105-192 fji high, a common size being 

 192 X 140 i".. The spores are borne on unbranched, persistent, 

 hyaline threads, and are continuous, hyaline, fusoid to ellipsoid, 

 i-celled with a highly refractive guttule at either end, and vary 

 in size from 7-14 X 3^ /t, a common size being 7 X 3^ m- 



