Volume 53, Issue 5
May 1961, pages 217-273
pp 217-229 May 1961
pp 230-239 May 1961
Three species of freshwater fishes, namelyO. punctatus, M. vittatus andB. stigma, were taken to establish the effect of temperature on the frequency of heart beat. InO. punctatus, experiments were made on three different size groups to illustrate the differences in the heart rate between older and younger individuals. The response of heart in all the species is very similar. The decrease in temperature is accompanied with a fall in the frequency of heart beat and its subsequent increase is followed by a steady rise. Younger individuals show greater susceptibility to temperature changes than the juveniles and the adults.
The temperature characteristics of the heart rate have also been studied by using temperature coefficients Q10 andμ. Both these coefficients have been found to vary and it is suggested that the heart rate like other biological processes of poikilothermous animals is dependent on an optimum range of temperature as both high and low lead to an inhibition of vital activity.
pp 240-256 May 1961
The root apices of ten species belonging to seven genera of the family Zingiberaceæ exhibit two types of structural configuration. Nine of them have independent initials for cap and plerome and a common protodermperiblem complex, while the tenth has common initials for all the tissues.
Where the cap is separate, there could be distinguished two initiating zones. The columellogen in the middle which fits into a concavity at the tip of the root body is characterised by cutting off cells only transversely to the front producing the columella. The other showing T divisions and concerned with the production of the rest of the cap is the peripheral region.
The origin of the endodermis is traced to an initiating zone common with the periblem, the endodermis-periblem complex.
The cyto-physiological state of the cells has great importance from the histogenetic point of view. Here also could be distinguished a quiescent centre to the root tip with the meristematic zone composed of actively dividing cells around and behind it. The characteristics of the cells composing these two zones are described. It is further emphasized that this aspect should also be studied in addition to the structural configuration to have a more complete picture of the apical organization.
pp 257-262 May 1961
Contrasted forms of terminal cells have been observed in certain taxa ofOlax, Capparis, Scaevola andVochisia. The exact morphology of intermediary cell forms could only be known by studying their ontogeny in detail. The resulting data would throw interesting information on the question of homology among various types of cells.
pp 263-273 May 1961