Volume 54, Issue 1
July 1961, pages 1-55
pp 1-11 July 1961
pp 12-16 July 1961
The present account deals with some aspects of floral morphology and embryology ofStrombosia ceylanica.
The ovary is inferior and unilocular. The placental column bears at its tip 4–5 circinotropous, tenuinucellate and unitegmic ovules.
A single hypodermal archesporial cell functions directly as the megaspore mother cell. The development of the embryo-sac conforms to the Polygonum type. The embryo-sac remains intraovular, but shows a tendency of slight growth at the chalazal end. It becomes filled with starch grains.
The wall of the another consists of three layers external to the glandular tapetum. Endothecium is fibrillar. Pollen grains are triporate, and are mostly two-celled, while a few are three-celled at the shedding stage.
pp 17-23 July 1961
Maize plants raised from seeds soaked in Bassia oil frequently produced semi-sterile ears. In one case the progeny of a semi-sterile plant consisted of (1) plants with the normal number of bivalents and (2) plants with a fragment chromosome in addition to the normal number. The behaviour of the extrafragment chromosome in meiosis has been studied in detail. The origin of the fragment chromosome is also discussed. It is regarded as formed by fragmentation of a normal chromosome. This is possible on account of the frequent occurrence of fragmentation and other structural chromosome alterations in maize plants raised from seeds soaked in Bassia oil. A kernel loss of about 25% has been observed in plants having an extra-fragment chromosome. There was no evidence of an effective mechanism for progressive numerical increase of the fragment chromosome. Instead it was found that there is a significant loss of the extra-fragment chromosome from one generation to another.
pp 24-44 July 1961
The paper deals with a collection of foliose and fruticose lichens collected by Mr. R. S. Rao and Dr. G. Panigrahi from Assam and North-East Frontier Agency of India. The total number as determined is 72 species under 18 genera and 9 families in a collection of about 145 specimens. Notable aspects of the investigations are the new reports from this region of the species—Cetraria asahinæ, C. straminea andUsnea asahinæ—and the discovery of the fertile state of the specimensAnzia physoidea andCetraria straminea which were so far known in the sterile condition only.
pp 45-55 July 1961