Cytological Studies in Four Species of Pithophora Wittr

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Four species of Pithophora viz. P. kewensis, P. zelleri, P. polymorpha and P. roettleri were collected from different localities of Ranchi and Muzaffarpur and their cytology has been worked out.
The nuclei at growing end cells have been found to be smaller, deeply stained and crowded than rest part of the cells. In all species at hand, except P. kewensis, abnormal nuclei of various shapes and sizes have been observed in addition to normal ones which are spherical. The number of abnormal nuclei are fairly high in older cells and they are very faintly stained, presumably due to poor chromatin material.
The diameter of interphase nuclei has been found to be inversely proportionate to the number of nuclei present in the cells. Form having low number of nuclei possesses bigger nuclei than those having comparatively higher number of nuclei. Such a correlation between the dimension and number of nuclei has not been reported so far in other genera of Cladophorales.
Nuclear division in P. kewensis has been observed exclusively mitotic while in rest of the three genera, it is accomplished partly by mitosis and partly by amitosis. Amitotic division takes place by furrowing and not by nuclear plate formation. It has been assumed that amitotic division in Pithophora is an adaptation to its week metabolic process. Further, it has been held that amitosis in this genus, may be compensatory to the absence of sexual reproduction and/or polyploidy and that it might have played a significant role in speciation of the genus.
Unlike other genera viz. Cladophora Kutz., Rhizoclonium Kutz. and Chaetomor-pha, mitotic nuclear, division in all the four species under study, is confined to a particular region of any cell and different stages i. e. from prophase to telophase in succession have been observed in a single cell.
Chromosomes at metaphase in each of four species at hand organize on an equatorial plate exceeding the diameter of interphase nuclei. Sticky nature of the metaphase chromosomes has been experienced consistently during the course of investigation and hence it seems to be a characteristic feature of the genus.
The chromosomes at metaphase have been counted as 24 in P. kewensis and P. zelleri and as 36 in P. polymorpha and P. roettleri. Chromosome number in three species viz. P. zelleri, P. polymorpha and P. roettleri has been reported for the first time whereas in P. kewensis, it is confirmation of earlier finding of Patel (1971). Since meiosis has not been ascertained so far in Pithophora, haploid or diploid nature of worked out chromosome numbers has not been expressed. Basic chromosome number as 6 has been suggested for Pithophora.