Current 378 Upwelling in the Region of the Science

sankaran (Atomic Energy Establishment). The Mr. S. C. Mehta (Indian Agricultural Research principles of the field emission and the field ion Institute) explained the mode of handling of microscopes were the subject of symposium specimens like spores and diatoms and the talks by Drs. Ramakhshna Rao and Bahadur. purification of viruses extracted from plants for Dr (Mrs ) Satyavati M. Sirsat (Indian Cancer electron microscopic study. Research Centre) started the course in biologi- The recent development of the thin autoradio- cal sciences with a lecture on the ultrastructure graphic emulsion with improved resolution and of the cell. She also gave two symposium the application of autoradiography to electron talks one on "Ultrastructural aspects of the microscopy were considered by Dr. P. N. Shri- Cancer Cell" and the second on "Macro- vastava (University of Rajasthan). Mr. S. D. molecules". Paiekar from the same University discussed the Dr. S. R. Bawa (Punjab University) discussed, methodology and applications of cytochemistry the preparation of tissues and sections of bio- at the ultrastructural level. logical material for electron microscopy. In a All the participants, irrespective of their symposium lecture (illustrated by a film pro- scientific background, had to undergo the jection) on "Organelles of Motility" Dr. Bawa practical course in the various techniques of indicated the usefulness of the instrument in specimen preparation in both physical and bio- unravelling the intricate details of the highly logical sciences and interpretation in the electron specialized organelles like flagella and cilia. microscope. Various experimental techniques like shadow The authors feel that the summer school in casting, ultra thin sectioning and negative electron microscopy, the first of its kind in staining in vogue for bacteria and viruses and , has more than fulfilled the object of the the preparation of macromolecules by the organisers.. pseudo-replica method for electron microscopic investigations were described by Dr. S. N. Chatterjee (School of Tropical Medicine). Dept. of Inorganic and H. MANOHAR. He also delivered a lecture on the Ultrastructure Physical Chemistry, of bacteria and viruses correlating structure Indian Institute of Science, with function. Drs. P. Sadhukhan and D. N. Bangalore-12, Misra (Saha Institute of Nuclear Physics) dis- cussed the different procedures of "particle Cytogenetics Laboratory, S. SUBRAMANYAM. counting by electron microscopy and its applica- Dept. of Biochemistry, tion in quantitative virology" and "the mass Indian Institute of Science, thickness of biological specimens". Bangalore-12,

UPWELLING IN THE MINICOY REGION OF THE ARABIAN SEA L. V. GANGADHARA RAO AND R. JAYARAMAN Planning and Data Division, National Institute of Oceanography, C.S.I.R., New Delhi

THE coral island, Minicoy (Latitude 8° 7' N, tunas in the central and equatorial Pacific by Longitude 73° 18' E), which is situated the Pacific Oceanic Fishery Investigations between the Laccadive and the Maldive (POFI) group. Archipelagos is a major tuna-fishing centre in In one of the International the Indian Ocean region.1 While the importance Expedition (IIOE) cruises in the Arabian Sea, of this region from the point of tuna fishery has INS KISTNA worked out a long: section of 15 been well recognized, we have very little data stations along the latitude 8° N from the 27th on the Oceanographic conditions prevalent there. November to the 2nd December 1962. During This is particularly noteworthy since in many the occupation of stations in the vicinity of areas, tuna investigations have always been Minicoy, it was particularly noticed by one of supported by large-scale Oceanographic studies.2 us (R.J.) that the ship was drifting considerably It may also be mentioned here that one of the giving rise to large wire angles indicating the most important discoveries in modern oceano- possibility of strong water movements in the graphy, namely the Cromwell Current, is area. In addition, while examining the distri- associated with, the systematic investigations for bution of various parameters along this 8° N No. 15 Aug. 5, 1966 Upwelling in the Minicoy Region of the Arabian Sea 379 section, some very interesting features were make a detailed analysis of the data for various observed in respect of stations in the Minicoy parameters in this region in particular (Stns region. It was, therefore, thought desirable to 84-81). The location of stations and the verti-

FIG 1 .Vertical distribution of temperature, salinity, density and dissolved oxygen along a section south of Minicoy Island during the last week of November, 1962: (α) Shows the location of station along the section, (b) Shows the temperature distribution-contour interval 1 C. (c) Shows the salinity distribution- contour interval 0·5‰. (d) Shows the distribution of density in terms of ^-contour interval 0·5 gm./litre. e) Shows the distribution of dissolved oxygen contour interval 1 ml/l. Current New Record of Foliar Sclereids in Three Dicotyledonous Genera Science 380 circulation for the period of observation. Dur- cal distribution of various parameters in the ing this period, the general set of current in upper 200 metres are shown, in Fig. 1 (α-e). the southern part of the Arabian Sea is westerly. At Stn. 82, the temperature structure shows Owing to the coastal conformation, a north- a sudden decrease in the thickness of mixed north-westerly current develops off the west layer and the presence of relatively colder coast of India. These two currents diverge in water in it. In association with this feature, a the vicinity of Minicoy leading to upwelling in sharp rise of thermocline to 50 m. depth is seen, this region. The relatively low saline lighter while in the neighbouring stations it is deeper water seen in the surface layers at Stns. 81-82 (75-100 m.)· The salinity distribution shows a may be the water possibly parcel of relatively low saline water in the carried westward by the north equatorial surface layers at Stns. 81-82 and the resulting current. local halocline is seen to be surfacing at Stns. 82-83. The density structure indicates the It is pertinent to point out here that according presence of a parcel of relatively lighter water to Jones and Kumaran (loc. cit) in the Minicoy in the surface at Stns. 81-82 with its westward area, tuna fishery is operative from September boundary being situated between Stns. 82-83. to April, the peak season being from December The isopycnals exhibit an upward tilt under to March. It is possible that the upwelling, Stn. 82 at 50-150 m. depth. The dissolved oxygen which has been observed during late November, content is seen to be less at 40-100 m. depth may have considerable impact on the peak tuna under Stn. 82 compared to its value under the catches of this region. The exact sequence of neighbouring stations at the corresponding events and the ultimate correlation between depths. The distribution of all these parameters these physical processes and the tuna fishery clearly indicate that upwelling is present at of Minicoy require more detailed investigation. Stn. 82, which is situated very close to Minicoy. The authors wish to express their deep sense The phenomenon appears to be limited to the of gratitude to Dr. N. K. Panikkar, Director, upper 150 metres. National Institute of Oceanography, C.S.I.R., Among the various factors examined with a New Delhi, for advice and encouragement. view to finding out the causes of this upwelling, the most obvious seems to be the presence of diverging current systems. As the observations 1, Jones, S and Kumaran, M , Indian J. Fish., 1959, were taken in the last week of November, the 6 (1), 30. typical circulation established for the earlier half 2. Schaefer, M. B., Rep. Calif Ocean. Fish., Invest., of the north-east monsoon season (November to (SS/16b and 22 MP/1b and 7a), 1961, 8, 41. 3. West Coast of India Pilot, Hydrography Dept., January) can be taken as the representative Admiralty, London, 1961.

NEW RECORD OF FOLIAR SCLEREIDS IN THREE DICOTYLEDONOUS GENERA A. N. RAO Department of Botany, University of Singapore, Singapore-10

IN order to select a few plants as experimental the foliar sclereids in these forms is presented materials for the morphogenetic studies of here. The leaf clearings, sections and macera- foliar sclereids, the leaf anatomy of certain local tions were prepared following the procedures dicotyledons was investigated. More than 200 previously outlined by Foster.1 species were surveyed this way, and in the Agrostistachya scssilifolia Pax unci Hoffm. is lamina of certain species, the sclereids were an unbranched or sparingly branched shrub, present. A reference to the earlier literature common in lowland forests of Malayan revealed that in most of them the presence and Peninsula. On top of the wiry stem a tuft, of distribution of foliar sclereids was either already elongated leaves are compactly arranged in a recorded or described. However, in . these whorl, with humus collection in the centre, three genera, Agrostistachys (Euphorbiaceae), giving a characteristic appearance to the plant. Taxotrophis (Moraceae), and Timonius (Kubi- An examination of cleared mature leaves shows aceae) the occurrence of foliar sclereids appears 1-3 that the sclereids are densely arranged and the to be unrecorded so far. A brief account on fibre-like individual cells are entangled with the cellular characters and distribution of one another (Fig. 1). Their relationship with