Considerable information about the cytology of triploids is available in genera such as Datura (Belling and Blakeslee 1922), Lycopersicon (Rick and Barton 1954) and Zea (McClintock 1929). Meiotic behaviour has been studied in only a few triploids of complete translocation heterozygotes. Sands (1925) was the first to see characteristic chains in diploid Rhoeo but interpreted them in terms of the synapsis theory current at that time. The present in vestigation is based on a study of meiosis in a spontaneous triploid Rhoeo, which made its appearance in a population of Rhoeo discolor seedlings.Seitz (1935) describes in triploid Oenothera, meiotic configurations containing from one to several chromosomes. Catcheside (1931) describes ring bivalents and rod chromosomes in a ring at the heterotypic metaphase in Oenothera pycnocarpa. Darlington (1929) reported that diploid Rhoeo had a circle of twelve chromosomes. In a spontaneous tetraploid Rhoeo discolor, Walters and Gerstel (1948) observed chains with 3-12 chromosomes. The present study of the triploid was initiated to compare the types of meiotic configurations produced in the triploid with those expected, with particular reference to the formation of trivalents and ring bivalents. The frequency of ring bivalents and long chains of chromosomes and the frequency of chiasma formation in the triploid will be compared with that of the diploid Rhoeo. Materials and methodsDiploid and triploid Rhoeo plants were grown in a green-house under the same con ditions. Material for cytological studies was collected and fixed in a solution of 3 parts absolute alcohol: 1 part glacial acetic acid. Antheres were squashed in iron aceto carmine. It was found that inverting the prepared slide over vapours of con. HNO3 gave better differentiation of chromosomes in some cases.Most microphotographs are of permanent preparations. The drawings were made with a Zeiss camera lucida. Meiosis in diploids and triploidsThe leptotene stage was rather obscure and the pachytene and diplotene stages were so sticky that it was not possible to follow the threads com Table 1. An analysis of metaphase configurations

Rate of feeding, asTime to Organism ml. water filtered 50 per cent per hr. clearance N auplii of Artemia salina, 0•75-1•0 mm. length 4-15 1½ hr.

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