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Electron micrographs show the presence of the polyhedral, the outer, and the inner membranes occurring in nuclear polyhedral bodies fromMalacosoma neustria, Barathra brassicae andAdoxophyes reticulana. The outer membranes appear to be composed of a central, bimolecular leaflet of lipids bounded on either side by carbohydrates and proteins. The polyhedral and inner membranes, however, seem to consist of protein only. The inner membranes are closely attached to the virus rods, and so are the polyhedral membranes to the polyhedral protein. De polyedermembranen vanMalacosoma neustria, Barathra brassicae enAdoxophyes reticulana, alsmede de buitenste en binnenste membranen om de deeltjes van deze kernpolyedervirussen, werden met de elektronenmicroscoop bestudeerd (fig. 1A-I, 2A-C). Om de polyeders te fixeren en ter verkrijging van bepaalde contrasten in ultra-dunne coupes werd van verschillende agentia gebruik gemaakt. Vergelijking van de verkregen foto's (fig. 2D-I, 3A-B) wijst uit, dat het buitenste membraan uit een bimoleculaire laag van lipiden bestaat, die aan beide zijden door koolhydraten en eiwitten zijn begrensd (fig. 4); de polyedermembranen (fig. 3B) bestaan evenals de binnenste membranen echter uitsluitend uit eiwitten. De virusstaafjes en de polyeders zijn respectievelijk door het binnenste membraan en door het polyedermembraan nauw omsloten.

Insect-to-insect transmission of potato leaf roll virus proved possible by injecting either juice or haemolymph from viruliferous Myzus persicae into virus-free ones. In serial transmission experiments, in which injection of haemolymph was practised, the virus could be carried through as many as 15 successive aphid-to-aphid passages without access of inoculated insects to any plants that are susceptible to leaf roll. The theoretical dilution of original virus used for the inoculation in the 15th passage would have been approximately 10−21. It is concluded that such persistence of virus in the aphids could only be explained on the assumption that the insect itself sustains reproduction of the virus. Zusammenfassung 1. Das Blattrollvirus der Kartoffel konnte durch Injektion von Pressaft oder Blut virusinfizierter Myzus persicae (Sulz.) auf virusfreie Insekten ubertragen werden. 2. Bei Serien-Ubertragungen unter Verwendung von Blutinjektionen blieb das Virus in 15 aufeinander folgenden Generationen ursprunglich virusfreier Blattlause erhalten. Hierbei wurde nach der Injektion als Zwischenwirt der blattrollunempfindliche chinesische Kohl benutzt. 3. Die theoretische Verdunnung der ursprunglichen Virusmenge pro Blattlaus betrug nach der 15. Passage ungefahr 10−21. Injektion des auf 1: 104 verdunnten Blutes virusinfizierter Lause ergab dagegen in keinem Fall Infektionsfahigkeit (Tabelle III und IV). 4. Die Existenz einer Latenz-Periode bei der Ubertragung konnte nach Injektion kleiner Virusmengen bewiesen werden. Verdunnung des injizierten Blutes verlangerte diese Periode (Tabelle I und II). 5. Diese Befunde deuten auf Vermehrung des Virus innerhalb der Blattlasen. 6. Wenn virusinfizierte Blattlause auf chinesischem Kohl gehalten werden, zeigt ihre Infektionsfahigkeit deutlich periodische Schwankungen (Fig. 1).

Positive reactions in micro-precipitation tests showed the serological relationship between theTipula iridescent virus (TIV) fromTipula paludosa andPieris brassicae. In gel diffusion tests, the results were negative. Applying the fluorescent antibody technique the first fluorescent particles in the proleucocytes and amoebocytes ofP. brassicae were observed on the third day after infection with TIV. On the seventh day the hemocytes having reached their maximum size, were swollen and completely filled with the viral antigen. In the healthy larvae of the same age, the hemocytes appeared to be normal.

The nuclear polyhedral bodies fromMalacosoma neustria are enclosed within a membrane. The diameter of the nuclear polyhedra varies from 0.9 to 2.8 μ with an average of 1.8 μ. In the nuclear polyhedra the rod-like virus particles occur both singly and in bundles. The single virus rods are enclosed within two membranes, namely the intimate membrane and the developmental membrane. The virus rods which occur in bundles have an intimate membrane just like the single virus rods, whereas the developmental membrane encloses the whole bundle. The virus rods are closely packed by the intimate membrane and between the intimate and the developmental membrane is a space. The diameter of the virus rods without membranes, determined from sectioned polyhedra, is about 25 mμ and the length 250 mμ.

Since potato leafroll virus multiplies in the green peach aphid,Myzus persicae, the effect of the virus on the biology of its vector was investigated. Observations were made regarding the longevity and the reproduction rate of viruliferous and non-viruliferous aphids on leafroll-diseased and healthy plants ofPhysalis floridana. The same matters were investigated for both viruliferous and non-viruliferous aphids on seedlings of Chinese cabbage (Brassica pekinensis). It was shown that on leafroll-diseased plants ofP. floridana the aphids produced more progeny than on healthy ones, although the average number of progeny produced per day in both cases was almost the same. On healthy Chinese cabbage seedlings there was no difference in average length of the larval and adult stages, number of progeny per aphid, and number of progeny per day, between viruliferous and non-viruliferous aphids. Evidence was obtained that the virus does not influence the development of its vector. Measurements of oxygen consumption of both viruliferous and non-viruliferous aphids point in the same direction.

In Laborversuchen mit Larven vonAdoxophyes reticulana, gezogen in einem Glaskasten auf Apfelblattern oder auf kleinen Apfelbaumen welche gespritzt wurden mit einer Losung eines Kernung Plasmapolyedervirus ausA. reticulana, zeigte sich das Viruskomplex sehr pathogen fur diese Larven.

Electron micrographs show the presence of DNA-cores in the virus rods isolated from nuclear polyhedral bodies fromBarathra brassicae, Adoxophyes reticulana andOrgyia antiqua. The DNA-cores in the virus rods are enclosed by virus protein.