Search

Although cultivated rice ( Oryza sativa L.) has been grown in the United States since the seventeenth century, it was not until 1912 that commercial rice production was practised in California. At present, approximately one quarter of the total annual U.S. rice crop is produced in the Central Valley of California. Due to the continually flooded conditions that prevail in Californian rice fields, the weed flora is highly specialised and is composed of some 62 species of aquatic vascular plants. The flora is unusual among crop weed floras of California in that it contains a substantial proportion (ca. two thirds) of native species. This is probably a result of the similarity in ecological conditions between rice fields and the original wetland habitats of the Central Valley that they replaced. Seventeen of the 20 alien species in the weed flora are of Old World origin and several ( Cyperus difformis L., Dopatrium junceum (Roxb.) Ham., Echinochloa crusgalli (L.) Beauv., Scirpus mucronatus L., Monochoria vaginalis (Burm. f.) Presl, Oryza rufipogon Griff., Ottelia alismoides (L.) Pers. and Rotala indica (Willd.) Koehne are widely distributed and well-documented weeds associated with rice. It is proposed that the most likely methody by which these aliens have been introduced to California is as seed contaminants of imported rice stocks. The small seed size, annual life form and autogamous breeding systems of the majority of these species probably aid in their dispersal, establishment and colonization of rice fields. A survey of 70 rice fields distributed throughout the rice-growing areas of the state indicated that the annuals Sagittaria montevidensis Cham. and Schlecht. ssp. calycina (Engelm.) Bogin., Ammannia coccinea Rottb., Bacopa rotundifolia (Michx.) Wettst. and taxa in the Echinochloa crus-galli complex are the most abundant and widely distributed rice weeds in California.

In the present paper vascular anatomy of the flower of all the three Indian species of Pontederiaceae,viz., Monochoria hastaefolia Presl,Monochoria vaginalis Presl andEichhornia crassipes Solms is described.

1. During the spring and summer of 1948, the synecological investigation was made by quadrate method on virgin soil, reclaimed land, rich farmland, and paddy-field at Kashii District (Fukuoka Prefecture). These places were composed of a strong acid soil originated from Tertiary. 2. Among these the following species grouped in (a) were abundant in strong acid soil and so might be called acid plants. While the species in (b) might be supposed as plants that were disagreeable with strong acidity of soil ; they were not as common on that soil though they were usually seen numerous in fertilized farm land as its indecator-plants: (a) Lespedeza striata H. A. Miscanthus sinensis Anderss. Melampyrum roseum Mxim. var. Japonicum Fr. etsav. Panicum sanginale L. Polygonum Blumei Meissn. Gnaphalium multiceps Wall. Alopecurus fubus Sm. Polygonum aviculare L. Monochoria vaginalis Presl. var. Plantaginea Solms. Lindernia angustifolia Wettst. Rotala indica var. Uliginosa. Eliocharis acicularis R. Br. (b) Eu phorbia pekinensis Rupr. Galium aparime L. Veronica polita Fr. Veronica peregrina L. Spirodela polyrhiza Schleid. Lemna paucicosta Hegelm 3. In order to quiken promote the maturing of the reclaimed land into rich farmland, cultivate of the following species as green manure or forage crop was advisable: Lespedeza striata H. et A. Panicum sanginale L. Arundinella anomala Steud. Pueraria Thumbergiana Benth. Cassia minoides L.

This article 'Rice Ragged Stunt Virus (RSV) in Aquatic Weed Monochoria vaginalis' appeared in the International Rice Research Newsletter series, created by the International Rice Research Institute (IRRI). The primary objective of this publication was to expedite communication among scientists concerned with the development of improved technology for rice and for rice based cropping systems. This publication will report what scientists are doing to increase the production of rice in as much as this crop feeds the most densely populated and land scarce nations in the world.

smuts on account of their rarity and the interesting types of lifecycles in many of the species. The rarity of these smuts is often due to the very obscure symptoms they produce on the host, which might range from an almost inconspicuous paling of the infected portions to definite discolored spots. In very few cases there is the formation of tumor-like excrescences on the host. In India, three species of Doassansia have been known by the determinations of Sydow and Butler. Another species, Doassansia Hygrophilae Thirumalachar, was added by the writer (1946). It is based on a collection of a leaf smut made near Nandi, Mysore, on Hygrophila sp. No species of Burrillia was hitherto known to occur in India, and a first report of an undescribed species of Burrillia, viz. B. Narasimhanii, was made recently by Thirumalachar and Mundkur (1946) on Alisma reniformis G. Don. This has been followed up by the finding of another species of Burrillia on Monochoria vaginalis Presl. by the writer and it appears to be undescribed. The life-cycle of the smut has been worked out in some detai.l, and in this paper an account of it is presented. Some of the observations made on the other species of Doassansia and Burrillia are also included.