Volume 9, Issue 1
January 1939, pages 1-61
pp 1-6 January 1939
pp 7-12 January 1939
pp 13-28 January 1939
pp 29-38 January 1939
The importance of studying the ultimate components of the panicle when engaging on the problem of yield is emphasised. The different types of panicles in sorghum are shown to arise from different possible combinations of the factors, length of rachis, the mode of variation of the primary panicle branches, the extent of ramification of panicle branching, the angle which the whorls make with the rachis, the secondary branch zone of the primary branch, and the density of clustering of fertile spikelets. Relationships are described between length of rachis and 4 types of panicle; length of rachis and maximum length of primary branch; number of primary branches and length of rachis; length of primary branch and secondary branch; total number of fertile spikelets and weight per grain; total number of fertile spikelets and the sum of the lengths of all the primary branches. The solution to the problem of yield must be based on the weight and size of an individual grain and the components which determine the number of fertile spikelets.
pp 39-48 January 1939
The paper is a detailed account of the prophasic changes in the nuclei of the microspore mother cells inScœvola Lobelia Linn.
The leptotene threads are beaded with clear diamond-shaped areas. It is therefore probable that the threads are double.
There are eight diplotene pairs and these are of different lengths. The nature and number of the chiasmata in these pairs are followed.
The late diplotene chromosomes show the presence of two coiled strands in specially favourable preparations.
The haploid number of chromosomes is determined from several countings to be eight; this number also corresponds to the number of diplotene pairs.
After the second division in the mother cells, the microspores are formed which show the typical tetrahedral arrangement.
The pollen grains are binucleate at the time of liberation from the anther locules.
pp 49-56 January 1939
Organogeny of the flower and structure and development of the anther and embryo-sac have been studied in some members of the Verbenaceæ. The development of the floral parts inStachytarpheta indica shows that the calyx differentiates before the stamens and the petals, and not after the stamens as has been described by Kanda (1923) inVerbena. Development of the anther and the pollen is quite normal. Cytokinesis takes place by furrowing. Tapetum is of the secretion type. The pollen grains are mostly spherical, but inStachytarpheta they are prominently three-lobed. The mature pollen grain is 3-nucleate. The ovule shows a single archesporial cell. No parietal cell is cut off and the archesporial cell directly develops into the megaspore-mother cell. A linear tetrad of megaspores is formed, of which the chalazal megaspore develops into the embryo-sac according to the normal type. The egg-apparatus has a normal structure and so is the behaviour of the polar nuclei. The antipodals are small and three in number, but inClerodendron Phlomidis they multiply by repeated divisions to form about twenty cells. The nucellus is of the typical sympetalous-type.
pp 57-61 January 1939
There are three pairs of U-shaped nephridia which occur in segments 4, 5 and 6.
A detailed description of the structure of the nephridia is given.
There are no nephridia in the middle and posterior segments. The genital products probably escape by rupture of the body wall.