Volume 23, Issue 6
June 1946, pages 249-317
pp 249-259 June 1946
Detailed studies on the initiation and development of axillary buds inHeracleum andLeonurus have been reported in this paper.
Works so far done on this problem in Ferns, Monocotyledons and Dicotyledons have been briefly reviewed.
In Ferns an axillary bud is initiated in thedetached (apical)meristem on the free surface of the axis or “in proximity to meristele conjunctions“. In Monocotyledons initiation takes place in the surface layer of thecorpus, on the side opposite to the insertion of, and in association with, the leaf primordium just above the one in Whose axil the bud appears. Hence Hsü (1944) describes the origin as ‘endogenous’ in Monocotyledons. In Dicotyledons though Goebel reports origin from the embryonal meristem a little behind the apex, Koch, Majumdar and Datta report origin in the vacuolating cells of the adaxial epidermis of the subtending leaf opposite the median bundle inSyringa, Heracleum andLeonurus.
In the shoot apices of Ferns, Monocotyledons and Dicotyledons leaf primordia are laid down first and buds are initiated in their axils later. A year may elapse between the laying down of the axillant leaves and formation of buds in their axils as reported in the winter buds ofSyringa.
Bud trace originates in the bud primordium and then differentiates backwards into theleaf- cushion outside the axial ring of vascular bundles, finally it enters the ring to unite with one of its synthetic bundles.
As the buds normally originate in the axils of leaves which are removed some distance from the apex and which are growing vigorously or unfolding, it is suggested that their initiation is due to some physiological processes than to any specific qualities inherent in the apical meristem.
pp 260-265 June 1946
The fruit flies show chæmotropic response. Citronella oil, ammonia vanilla and clensel were tried but none of them yielded satisfactory results. Clensel, however, had a slight advantage over others.
Clensel when tried in 1:30 dilution gave higher percentage of the attraction as compared with other dilutions.
On an average,D. ferrugineus predominated over other species in the collection during the entire period of four years.
Males were captured slightly more in numbers but the differences between the males and females were in no way significant.
Clensel even when tried on a very large scale did not help in reducing the damage by fruit flies to any appreciable extent and much less economically. For economy trap bottles should be kept at a distance of 30 ft. even though better results were obtained at 15 ft.
pp 266-273 June 1946
For the study of hybrid vigour two varieties differing very widely from each other Were chosen. In the cross between the varieties Udipi as the female parent and Raviya as the male parent, it has been observed at the very outset that the immediate effect of crossing manifest itself in the increased weight of the F1 seeds. TheF1 seeds had a slightly higher percentage of germination than that of the parental strains.
The F1 seedlings and plants exhibited better vigour than the parental seedlings from the very start. The cross resembled the male parent with respect to the fruit characters.
The thorny character of the female parent was totally absent in the case of the hybrid plants.
The hybrids flowered earlier than the earlier parent by 18 days, and yielded more than both the parents, the increase in yield being 17·2 per cent., over the better parent and 24·1 per cent., over that of the poorer parent.
Other observations with regard to plant and fruit characters are detailed in the text.
The importance of hybrid vigour in the brinjal crop improvement is therefore indicated.
pp 274-280 June 1946
pp 281-300 June 1946
Diploid chromosome numbers for 38 uninvestigated species ofScitamineæ have been recorded together with a description of their morphology.
The frequency of chromosome numbers for the different members of this order has been studied.
Indirect evidence has been adduced to show that most of the high chromosome-numbered species of this order are in the nature of polyploids.
Aneuploid numerical relationships has been met with in the chromosome numbers of not only the different genera but also within the species of the same genus.
The two big chromosomes seen regularly during prophase in the root-tip cells ofCalathea medeo-picta are interpreted as compound structures and the occurrence of 23 chromosomes in some cells of the root-tip has been postulated.
Primary basic numbersn = 4, 5 and 6 and secondary basic numbersn = 9, 10, 11, 12 and 13 have been suggested for the order.
A phyletic scheme showing interrelationship among the members of this order on the basis of chromosome numbers and chromosome size has been included.
pp 301-311 June 1946
pp 312-317 June 1946
No single explanation of tonus in unstriated muscle can suffice as there are two kinds of tonic contractions, one with and the other without oxygen usage. The former is akin to ordinary contraction and the latter to some structural change in muscle. It is suggested that in tonic contractions without oxygen usage, myosin forms a stable compound with some ions in the muscle fibres, while in twitch such a compound is unstable. The two factors which combine with myosin to form the contractible compounds of tonic and twitch contractions respectively are mutually exclusive in their combination with myosin; this explains many tonic and twitch phenomena in unstriated muscle.