The morphology of the root system of Chondrilla juncea and its response to changes in soil type near Wagga Wagga, New South Wales, is described. The root system is described as consisting of vigorous long roots capable of vegetative reproduction at any depth and short roots, apparently without secondary thickening, of limited life span. The long root system consists of a simple tap root and a number of surface laterals, which increase in frequency and extent of lateral spread as soil clay content decreases. The relationship between plant age, growth stage, and depth of origin, as well as depth of planting and soil type, on shoot production from root fragments also was studied. Root fragments from depths to 80 cm and more did not differ appreciably in regenerative capacity. But, whereas shoot buds formed on some seedling roots two to four weeks after germination, all such roots formed buds five weeks after germination. Soil type and depth of planting did not affect shoot production from root fragments per s e, but establishment of new plants fell as depth of planting increased. A comparison of vegetative and reproductive plant roots of similar age showed that regenerative capacity was minimal during the reproductive growth phase. The inhibition of shoot bud formation on the roots, however, was confined to the proximal 40 cm. It is suggested that weed control operations are likely to be more effective when carried out shortly after stem initiation than at other times.

The relationship between seed colour and viability and also the effect of seed age, moisture stress, depth of seed burial, and soil type on the germination of skeleton weed (Chondrilla juncea L.) were studied at Wagga Wagga, New South Wales. As the developing seeds matured their colour changed from greenish-white through yellow to yellow-brown or olive-green. Some 25 per cent of the yellow seeds were capable of germination but then only for a short period after shedding. Fully coloured, mature seeds showed 80 to 90 per cent germination capacity and remained viable for two to three years when stored in open containers. A few samples were dormant for about 12 weeks but the majority germinated rapidly when ample moisture was available. Germination was delayed and decreased with increasing water stress. Soil type had no apparent effect on germination but emergence was inversely related to depth of planting. There was no emergence from below 13 mm (1/2 inch) in heavy clays or 38 mm (19 inches) in other soils. Surface sown seeds did not establish readily on compacted surfaces, emphasizing the importance of the cultivated fallow in increasing the rate of spread.

A study of material from unstressed plants of Chondrilla juncea L. revealed a genetically based sterility in 3-4% of the achenes. Embryogeny is of the Asterad type but the basal cell cb divides horizontally before the vertical division in ca. Polyembryony occurred but seems rare; probably only one embryo in each ovule reaches maturity. The endosperm was nuclear at first, becoming cellular after a number of free mitoses. The outer layers persist in the seed. The uniseriate endothelium develops a persistent cuticle on its inner face, which becomes closely appressed to the remaining endosperm layer as the endothelium degenerates. Endosperm formation was erratic and independent of embryogeny. Because of the presence of aborted embryos associated with a well-developed endosperm, it is suggested that the degeneration is the result either of later formation of the endosperm or of unusually early cutinization of the endothelium.

Comparative experimental re.sults with dalapon-sodium and paraquat for the control of barley grass {Hordeum leporinum Link) in lucerne and subterranean clover pasture are reported. Sprays were applied 3-4 days after a simulated grazing..\t all rates tested (1-4 Ib/ac), dalapon provided satisfactory control of, but did not eradicate, barley grass. Subterranean clover productivity was reduced substantially whether application was in May or July; lucerne growth was retarded by 4 Ib/ac applieti in July.Paraquat applied at 0-06-0-25 Ib/ac in May gave similar bul somewhat less effective control than did dalapon. Some re-establishment of barley grass occurred as a result of late germinations following the May applications. Paraquat applied in July ai 0-06 Ib/ae gave unsatisfactory results, bui at 0-12 and 0-25 Ib/ac the control was comparable with that given by dalapon. Subterranean clover was damaged slightly by the May treatments but recovered quickly, after initial scorching, following applications in July. Lucerne was neither damaged nor retarded by paraquat.The addition of a wetting agent increased the efficacy of paraquat in controlling certain more tolerant annual grasses, but not barley grass. Dhherbage sHeclif des pdtures el des luzerrus: lutU conlre I'orge des liivresResume. L'auteur rapporte les rdsultats obtenus dans des experiences mettant en comparaison le dalapon sel de sodium et le paraquat pour la luite contre I'orge des liivres {Hordeum leporinum Link] dans la luzenie et des paturages de trifle souterrain. Les traitements ont ^te appHqu^s 3-4 jours apr^s une pature simul^e.A toutes les doses essayees (1,1^,4 kg/ha) le dalapon a donnd un d^sherbage satisfaisant mais pas une destruction complete de I'orge des iievres. La productivite du trcfle souterrain fut notablement r^uite, que le traitement ait 6i6 effectu^ en mai ou en juillet; la croissance de la luzeme fut relardee par une dose de 4,4 kg/ha appliquie en juillet.La paraquat appHqu^ de 0,07 k 0,28 kg/ha en mai, donna des rtsultats similaires bien que l^g^rement infdrieurs a ceux obtenus avec le dalapon.Une r^infestation d'orge des Iievres fut observ^e, resultant des germinations apr^s les traitements de mai. Le paraquat appliqu^ en juillet a 0,07 kg/ha ne donna pas de r^sultats satisfaisants, mais & 0,13 et 0,28 kg/ha le d^sherbage fut comparable k celui obtenu avec le dalapon.Le trefle souterrain fut endommage Increment par les traitements de mai; il r^cuptfra rapidement apr^s une reaction initiate, a la suite des applications en juillet. La luzerne ne fut ni endommag^e ni retardde par le paraquat.L'addition d'un mouillant aecrut I'efficacild du paraquat contre certaines gramin^es annuelles moins sensibles, mais pas contre I'orge des Iievres. Bekampfung von Hordeum leporinum auf Weiden und in Luzeme Zusammenfassung. Es wird tiber Versuche zur Bekampfung von Hordeum leporinum Link in Luzerne und auf Weiden mit Paraquat und dem Natriumsalz des Dalapon berichtet. Gespritzt wurde drei bis vier Tage nach simulierter Beweidung. Bei alien untersucbten Au...

The response of wheat to the length of fallow, to the number of cultivations, and to pre-planting chemical control of weeds on high fertility soils was determined under winter rainfall conditions at Wagga Wagga, New South Wales, over four years commencing 1960-61. Length of fallow had little influence on the conservation of rainfall except in 1961-62, when approximately twice the average summer rainfall added 1.8 inches of soil moisture per acre 48 inches. Long fallow increased available nitrogen accumulation, but this did not increase yield over either the mechanically prepared shorter fallows, or pre-planting chemical weed control. This was due to losses during the autumn-winter period of some of the excess mineral nitrogen that accrued during the long fallow. High mineral nitrogen concentrations also occurred during the summer on weed-free, uncultivated soils. Grain yield after a single autumn cultivation was as high as after a long fallow except in 1961-62. In this year the long fallow (September to May) significantly increased yields over all other treatments. The absence of any positive yield response to the application of 60 to 80 lb nitrogen an acre to short fallows suggests that mineral nitrogen concentrations were generally adequate for grain production. The addition of nitrogen to long fallows often depressed yields. The dependence of grain yield on adequate weed control is illustrated by a highly significant negative correlation (r = -0.849 ; P<0.001) of grain yield with weed growth. It is concluded that in the Wagga Wagga environment weed control is more important than moisture conservation and mineral nitrogen accumulation through fallowing.