H.—34.

6. Vegetative Cover in Relation to Soil Types. Some preliminary work has been carried out and arrangements made for co-operation with the Soil Survey Division, the Whangarei areas being dealt with first. 7. Leguminous Plants. A book is in preparation on the important legumes of New Zealand, somewhat on the lines of the book on grasses already published. 8. General. Miss Mason has charge of the seed herbarium, and has already increased its scope and usefulness as an aid in researches on weeds and other plants. Taxonomic and ecological studies have been made on both introduced and native species as time and opportunity have permitted, and several papers are in the press or have been submitted for publication. Mr. Zotov's important paper, in collaboration with others on the vegetation of the Tararua Ranges, has appeared and attracted considerable attention. He has also studied the grasslands erosion problems of the Kaimanawa and adjacent ranges. 9. Publications. During the year the following have been published : — " Fruit Characters in an Artificial Coprosma Hybrid." (11. H. Allan.) " Remarks on Hybrids between Leucogenes and Raoulia." (11. H. Allan.) " Germination of Ragwort-seed in Water." (A. L. Poole.) " Survey of the Tussock-grasslands of South Island." (V. D. Zotov.) " Vegetation of the Tararua Ranges." (V. D. Zotov and Others.) " Vegetative Propagation of Ragwort." (D. Cairns.) Submitted for publication are : — " The Grass Genus Puccinellia in New Zealand." (H. H. Allan and P. Jansen.) " Notes on Floristic Botany No. 7." (H. H. Allan.) " A Handbook of the Naturalized Plants of New Zealand." (H. H. Allan.) " Natural Hybridism in relation to Taxonomy." (11. H. Allan, in a book to be issued in England under the title, " The New Taxonomy.") PLANT DISEASES DIVISION. Director: Dr. G. H. Cunningham. Though the new laboratory and office buildings were not completed till the end of March, 1939, they were sufficiently advanced to permit of the transfer of the staff from Palmerston North in February. All the staff are now at the new headquarters at Owairaka (Mt. Albert), Auckland, with the exception of one officer, at Palmerston North and Lincoln respectively. Mr. W. D. Reicl was granted leave of absence for a further period of twelve months to enable him to complete his studies at the University of Edinburgh. 1. Plant Diseases Investigations. (a) Brassica Diseases. (1) Dry-rot. —This disease of swedes and turnips, due to the fungus Phoma lingam, has been further studied during the year. It was isolated from seedlings of marrow-stem kale, a first record of early infection on this host. The fuugus has been isolated from moist soils two months after infected plants were removed, but has not been recovered after a further period, showing that the organism does not persist in the soil for long unless associated with plant tissues. Further test of seed disinfectants were carried out to ascertain if some more effectual process than the standard hot-water treatment was available. Organic mercury and copper oxide dusts, calcium nitrate, and lime sulphur steep proved ineffectual. Plants sprayed with bordeaux mixture before being inoculated with spores of the organism remained free from disease. Bordeaux may therefore prove effectual in protecting brassicas being grown for breeding and other experimental purposes. (2) Club-root. —The proprietary product " Brassisan " is being tested on both a plot and field scale for control of club-root, due to the myxomycete (Plasmodiophora brassicae). Preliminary trials showed that while it exercised some measure of control, a considerable number of plants became infected in the trial areas. Four strains of rape, selected for their resistance to the disease, have been seeded in small isolated plots. Approximately .1 lb. of seed has been secured from each. Also there has been harvested F t seed of reciprocal crosses between two strains of club-root-resistant rape. Seed front.crosses of cabbage X broccoli, resistant to the disease, has also been harvested. Yield trials with resistant strains of rape and swedes have been sown at Palmerston North, Te Kuiti, Gore, and Invercargill. In some are being tested, additionally, manures which have been found by past work to reduce infection. (3) Diamond-bach Moth. —At Owairaka there have been carried out a series of tests with arsenates, derris, and nicotine sprays and dusts for control of this pest. Results were inconclusive owing to the small amount of infestation. A second block of late summer cabbages has been planted so that the work may be continued. As heavy infestation is present on these, further trials are being undertaken.

28