Volume 56, Issue 1
July 1962, pages 1-76
pp 1-12 July 1962
pp 13-26 July 1962
The six genera of the Vitaceæ studied show varying extent of perichalazal growth after fertilization. Ingrowths of rumination are produced by the integumentary tissues as a result of localised growth from the raphe region at the ventral side of the seed and their location in the mature seed is determined by the extent of perichalazal growth. InLeea the perichalaza itself becomes pushed in as an ingrowth and in addition to this four more ingrowths are produced; inCissus, Vitis, Tetrastigma andAmpelocissus the number of ingrowths is only two and these are situated away from the perichalaza; inCayratia the ingrowth is a single dome-shaped structure with two small longitudinal ridges at the inner face.
The nucellus increases after fertilization, and becomes ruminate by the ingrowths of the seedcoat. The endosperm remains quiescent and of small volume until the seed attains almost its mature size, but thereafter grows rapidly and replaces all the nucellus, thereby acquiring the same ruminate configuration. The mature endosperm contains fatty reserves and one druses in each cell.
The mechanical tissue of the mature seedcoat is completely derived from the innermost layer of the outer integument and is of varying layers thick in the different genera. The middle layers of the outer integument become tanniferous to varying extent in the different genera. The innermost layer of the inner integument becomes tanniferous, the outermost becomes spirally thickened and these two persist in the mature seed, whereas the middle layer acts as a nutritive layer and becomes completely crushed. Raphides occur in the seedcoat of all the genera exceptLeea.
pp 27-34 July 1962
pp 35-50 July 1962
pp 51-55 July 1962
The cytology ofM. longifolia (Linn.) Huds. 2n=18 and its two hybrids withM. cordifolia andM. piperita is presented. A plant received asM. longifolia (Linn.) var.royleana was found to be a natural hybrid betweenM. longifolia (Linn.) Huds. 2n=18 andM. cordifolia 2n=36 and had chromosome number 2n=27. A plant collected from Baniahal with 2n=33 was found to be a natural hybrid betweenM. longifolia (Linn.) Huds. 2n=18 andM. piperita Linn. 2n=48. The production of natural hybrids betweenM. longifolia (Linn.) Huds. and other species of mints is encouraged by the occurrence of male sterile plants which act as female parents.
pp 56-76 July 1962
This paper describes the anatomy and histology of the axis ofI. coromandelina and nine other species. They are similar in the vascular structure of the axis with the stele differentiated into an upper stem stele which sends off leaf-traces and a bi-, tri- or tetra-radiate rhizomorphic stele which gives off only root traces and consisting of its own basal meristem. The xylem elements in the centre of the stele are surrounded by a few layers of parenchyma, have no differentiation into proto- and meta-xylem. The xylem elements are then surrounded by irregularly arranged primary phloem possessing pit-like recesses on all the walls. The peculiarity of the cambium lies in its origin outside the primary phloem and the absence of intrafasicular cambium. It cuts off secondary parenchyma towards the outer side and some mixed tissue towards the inner consisting of specialized sieve cells and parenchyma. However, in some axes ofI. coromandelina, I. malenverniana andI. asiatica a few peculiarly oriented lignified cells are occasionally observed. The sieve cells of the secondary phloem consists of white glistening walls, clear contents, callose deposits around the sieve pores and absence of nuclei and starch grains which are of common occurrence of other cells ofIsætes. The presence of callose in sieve cells and lignin in lignified cells has been confirmed by several chemical tests.
A critical review of the previous literature has shown the existence of four school of thought regarding the nature of the secondary tissue. In absence of concrete evidences for assigning this tissue as secondary parenchyma, secondary xylem or secondary phloem the term ‘prismatic tissue’ has been retained as suggested by Russow (1872).