Cytomorphological observations were made on  an  induced  tetraploid   clone,  an evolved triploid clone and a diploid clone of Hevea brasiliensis (Willd.  ex. Adr.  de Juss.) Muell. Arg. Both the tetraploid and the triploid had varied number of leaflets, large floral parts and stomata and  thicker leaflets  compared   to those of  the diploid. In growth and morphological  features at the early stage  of  growth, the  triploid  appeared to be  inter­ mediate between the diploid and the tetraploid. Meiotic studies of the tetraploid showed large number of bivalents, while frequency of univalents,  trivalents and  quadrivalents was comparatively  low.  The triploid exhibited univalents, bivalents and trivalents. Anaphase I showed unequal segregation and formation  of  laggards  and  micronuclei in  the tetraploid and the  triploid,   the  frequency of  their  occurrence being more  in the  triploid.    Pollen stainability was very low in the triploid.

The  ozone  resistance  of  blends  of  natural  rubber  (NR)  and  ethylene/propylene  rubber (EPM) was quantitatively assessed in terms of critical stress-strain parameters.    The effects of blend ratio and addition of carbon  black and china clay on ozone resistance were also studied. It is observed that resistance of NR vulcanisates to ozone cracking is remarkably improved by blending it with EPM rubber.    A blend ratio in the range of  80: 20 to 70: 30 NR : EPM  is found  to give adequate  protection  against ozone attack. Addition  of high abrasion furnace (HAF)  black improves ozone resistance of NR and the blends.  Blending of HAF black masterbatches  of the two polymers is beneficial only when the proportion of EPM is more than 30 parts per hundred rubber (phr).    Addition of china clay  reduces ozone resistance  of  natural   rubber and  the  blends  drastically.

Nursery evaluation of sixty three genotypes of Hevea, obtained from 1982 hand pollinations was carried  out  for  yield and  related  characters  like plant  height,  girth,  number  of latex vessel rows and  bark  thickness. Simple, partial  and  multiple correlations of the variates were estimated.    Yield on test tapping was positively correlated with all other characters. Plant height showed significant correlation with girth. Girth and number of latex vessel rows showed significant positive correlation  with bark  thickness. Studies on partial  correlation revealed that number of  latex vessel rows is the  most important  character influencing the nursery yield.    The characters studied could explain 43 per cent of yield variability in  the  nursery  stage.

The characters  of petiolar  stomata  and  the leaf retention  percentage after  the incidence of  Phytophthora leaf fall disease in  Hevea brasiliensis (Willd. ex Adr.  Juss)  Muell.  Arg. was studied  in six  Hevea clones.   Considerable differences between disease resistant  and susceptible groups of clones were observed for leaf retention percentage, no. of stomata/10 mm² length of stomatal  aperture  and aperture  index. Leaf retention percentage  had  negative correlations  with  no. of stomata  /10 mm²  (P<0.01),  length of stomatal  aperture  (P<0.05) and  the aperture  index (P<0.01). Partial and multiple correlations  showed   the  importance of the frequency of petiolar stomata  and  the aperture  index as criteria  for selection of disease resistant clones.   About 68 per cent variation in leaf retention after the incidence of Phytophthora leaf fall disease could be explained  by the characters  of petiolar stomata.

The population of bacteria,  fungi and actinomycetes in fifteen rubber  growing soils was estimated. The occurrence of actinomycetes antagonistic to Phytophthora meadii (Mc Rae) and the extent of inhibitory activity were studied. In general, the population of bacteria was more than that of both fungi and actinomycetes and they varied widely in different soil samples. All soil samples, irrespective of  the  pH  and microbial population, harboured actinomycetes antagonistic to P. meadii and majority of these isolates  had inhibition zones upto 15 mm when tested by cross streak  assay. Inspite of the presence   of such large number of actinomycetes antagonistic to P. meadii, various diseases caused by this pathogen reoccurred every year.

The paper analyses  the seasonal  variations in rubber prices. The analysis showed that the seasonal index was the highest in July and the lowest in  December.  Production of rubber showed marked seasonality. The  analysis of  price in relation to production and consumption  showed that seasonality in prices was not  much pronounced  during  months in which production change was predominant,  which in turn point to the possibility of oligopsony in the buying market. During the peak production period, consumption  was found to fall resulting in low prices.  This necessitates the need for buffer  stock  operations so as to buy and store excess supplies and hold them off the market in times of falling prices and  release them when the prices rise. The producer is benefited by stabilisation of his income and  the manufacturer  through an assured supply of raw material.