Volume 14, Issue 5
November 1941, pages 1-488
pp 1- November 1941 Erratum
pp 437-453 November 1941
The percentage of parasitism in cotton fields is apparently too low to exercise any adequate control ofPempheres. Their numbers are extremely insufficient for the purpose. The host-parasitic ratio is capable of being improved by artificial multiplication and timely liberation of at least one species—Spathius critolaus. Beneficial results may follow this procedure. The more promising line of action, however, is to introduce into cotton fields the parasites of its pre-economic habitat by direct importation of parasitised material as also by laboratory breeding and manipulation, should the species prove amenable in this regard. Success in this or any similar project can never be assured. Attempts in these directions are desirable.
pp 454-460 November 1941
The haploid chromosome number was determined from the metaphase plate of the heterotypic division to be 20.
The uninucleate microspore gives rise to two definite cells following nuclear division, the generative cell and the tube cell. A clear space appears between the two cells, their adjacent cell membranes disappear and the generative nucleus shifts itself back and is engulfed into the tube cell.
The individuals of the quartet do not separate, but remain intact.
Pollinia germinate only after pollination. The tube nucleus elongates in the pollen tube upto 80 to 90 microns. The nucleolus of the tube nucleus occasionally undergoes fragmentation.
The generative nucleus divides in the tube to form two male nuclei.
Cyst formation at the tip of the pollen tubes is of common occurrence and development of plugs within the pollen tubes has been observed in many cases.
pp 461-465 November 1941
The development of the female gametophyte and endosperm formation inEriodendron anfractuosum has been studied.
Ovules are bitegumentary, anatropous with a zig-zag micropyle. The archesporium is hypodermal, and cuts off a parietal cell. Development of more than one archesporium has been observed.
The four megaspores formed are arranged as T-shaped tetrads.
The development of the embryo-sac conforms to the normal type. Antipodals show early degeneration.
A case of embryo-sac reversal has been noticed.
Endosperm is nuclear, and during post-fertilization stages the chalazal end becomes haustorial in function.
The floss is formed from the inner epidermal layer of the carpel. The cells of the floss are binucleate.
pp 466-471 November 1941
The fungus attacks leaves and sometimes twigs. The infected portions appear as concentric blotches. Three spore forms,viz., pycnia, æia and telia are present.
Pycnia are subhypodermal-flask shaped and orange yellow in colour. The paraphyses are exserted from the ostiole.
Aecia are developed on both the surfaces of the leaves, and are covered with well-developed peridia. Aeciospores are polyhydral and smooth-walled. A single germ pore becomes visible during germination.
Telia are amphigenous and are black in colour. Teliospore is stipitate, and two-celled. Spores germinate without a period of rest. The basidiospores are thin-walled, and uninucleate. Some abnormal types of germinations have been described.
Basidiospores infect the same host and form pycnia and æcia, and thus it is manifest that the fungus is autœcious.
Spore measurements and other considerations goes to show thatAecidium leiocarpum Syd. is the æcial stage ofPuccinia leiocarpum (Syd.) Thirumalachar. In conclusion the author wishes to acknowledge his indebtedness to Dr. M. A. Sampathkumaran,m.a., ph.d., Professor of Botany, Central College, Bangalore, for guidance and encouragement in the course of this work, and to Dr. B. B. Mundkur, Imperial Agricultural Research Institute, New Delhi, for the help given in identifying the species and valuable suggestions.
pp 472-488 November 1941
The development of the microsporangium ofPortulaca tuberosa, Roxb., is described. Multinucleate tapetal cells and tapetal nuclear fusion are met with.
The diploid number of chromosomes was found to be 18, which was confirmed by the meiotic counts. Diploid chromosome numbers of two other species ofPortulaca are also recorded for the first time.
Meiosis is normal and the microspore is two-celled at the shedding time.
Development of the ovary and the ovules is described in some detail. Embryo-sac formation and embryo development are of the normal type.
The possible meaning of the tapetal nuclear fusion is discussed from the view-point of the nutritive function of the tapetal cells.
The importance of recounting morphological details in spite of their repetition, is discussed in the light of observations recorded in this paper. The position ofPortulacaceœ is considered cyto-taxonomically.