• Volume 48, Issue 5

November 1958,   pages  211-258

• Inter-petiolar stipules ofGalium mollugo L

The inter-petiolar stipules ofGalium mollugo are separate, leaf-like in shape and size, and also in the possession of a single trace bundle. Morphogenetical studies at the shoot apex show that the initiation and vascularization of the leaves and stipules are different. Only the leaves bear axillary buds; the leaf-like stipules do not bear them. The foliar foundations by their union form acollar round the axis, from which it separates by the differentiation of a separation layer in its adaxial surface. The glandular hairs also arise from this layer. The axis on its separation shows a wavy contour of its surface. The crest of each initially shallow wave is occupied by a meristem which helps in the development of each ridge. From later behaviour of the apparently single leaf-trace bundle it appears that it is composed of three bundles and the laterals are concerned with the origin of the stipules and their traces.

• Studies on foliar sclereids in dicotyledons - VI. Origin and development of terminal sclereids in the leaf ofNiebuhria apetala dunn

An ontogenetic study has revealed that sclereid initials inNiebuhria apetala are terminal or subterminal to the procambial strand. The origin and sequence of formation of terminal sclereids have been found to coincide with the maturation of veinlets in the young leaf. The sclereids and veinends follow a distinct combination of centripetal and centrifugal pattern of initiation and maturation.

• On post-embryonic stages of phyllopod crustaceans,Triops (APUS),Streptocephalus andEstheria

• ISO-chromosomes and the origin of triploidy in hybrids between old and new world species ofPhiladelphus

1. AllPhiladelphus species in nature are diploids 2n=26.

2. The chromosome complement of species examined was found to be fairly uniform in morphology and could be represented by the haploid formulæ.$$1 L_m + 8 M_{st} + 2 S_{st} + 2 S_{sm} .$$

3. The L chromosome inPhiladelphus was found to be an iso-chromosome with a weak centromere.

4. While geographical isolation inPhiladelphus has not appreciably affected pairing between the 12 pairs of chromosomes in hybrids, it has a distinct effect on the pairing of iso-chromosomes.

5. Pollen fertility of species and hybrids is related to the behaviour of iso-chromosome.

6. Triploidy in interspecific hybrids is due to the formation of unreduced gametes by non-separation of iso-chromosomes at meiosis.

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