No abstract

Sterilit~t einer Artkreuzung" werden oft zwei vollkommen verschiedene Arten yon Sterilitat verstanden.In dem einen Falle wird iiberhaupt keine Bastardzygote gebilde~, Die Gameten der beiden Elternarten werden auf irgendeine Weise an der Durchfiihrung ihrer Funktion, der Befruchtung, gehindert. Die Kreuzung der beiden Arden ist nicht durchfiihrbar, d.h. die Kreuzung is~ mehr oder minder steril.In dem anderen Falle gelangen die Gameten zur Verschmelzung, und es wird eine Bastardzygote gebilde~. Abet die ontogenetische Entwicklung der Bastardpflanzen lauft nich~ harmonisch ab, sondern wird zu irgendeinem Zeitpunkte gehemmt. Dadurch werden die Bastardpflanzen ganz oder auch teilweise Iortpflanzungsunfahig, da sie gar keine oder nur mehr oder weniger funktionsunfahige Reproduktionsorgane bilden, d. h. die Bastardp/lanzen sind mehr oder minder steril.Wit wollen uns im folgenden nur mit der Sterilit~t der Bastardpflanzen befassen.Die Erkl~rung fiir das Auftreten yon Entwicklungsst6rungen der Bastarde sieht man meistens in einem )Iichtzusammenlaassen der Genome der beiden Elternarten und einer daraus sich ergebenden Unausgeglichenheit der Bastardgenotypen. Dieses Nichtzusammenpassen der elterlichen Genotypen kann auf zweierlei, yon genetischem StandpunkCe verschiedene, Art und Weise zustande kommen. Entweder harmonieren die Elterngenome als Ganze nicht miteinander, wodurch sich die Ent-wicklungsstSrungen schon bei der Entwicklung des diploiden Somas der 1 Die vorliegende Arbeit wurde im Bussey Institute, Harvard University, mit Unterstiitzung des International Education Board, New York, nnd im Kaiser-Wilhelm-Institut fiir Biologie mit Unterstiitzung der Notgemeinschaft der deutschen Wissensehaft durchgefiihrt. Herin Professor EAs~ und Herrn Geheimrat Co~.Ns mSehte ich auch an dieser Stelle meinen ergebensten Dank aussprechen.

No abstract

The present paper gives some observations on the tumour formation and other abnormalities observed in the interspecific hybrids, Nicotiana glauca x N. Langsdorffii and N. glauca x N. Sanderae. Without entering into a detailed discussion of the literature and the various speculations proposed by Kostoff and Whitaker about the causes of tumour formations or on the relations between "spontaneous" and pathogenic tumours (Kostoff, Levine and others), two new observations are described. 1) The abnormalities in the two above mentioned hybrids are quite different. As already reported by other authors, the hybrids N. glauca x N. Langsdorffii are initially quite normal and vigorous, while tumours and other proliferations, on the stem, the stem base and the root appear more or less frequently in older plants. Tumours on leaf are rare and flowers are normal (fig. 1,2,7 and 10). The hybrids N. glauca x N. Sanderae are very different from the former. These remain either weak and rachitic, forming early large tumours at the stem base and on the root (fig. 5 and 6 right half). Numerous shoots with more or less normal leaves may arise from these tumours (fig. 11 and 12). Or the plants show an extremely vigorous and abnormal ramification with a number of serial axial shoots developing in each leaf axis (fig. 3 and 4). The leaves are frequently deformed and the flowers exhibit abnormally coloured patches. When crossing N. glauca with F1 (N. Langsdorffii x N. Sanderae) the offspring could clearly be divided into two groups : plants exactly as described for N. glauca x N. Langsdorffii and others which correspond to the types of N. glauca x N. Sanderae. Thus it seems that we are dealing with a monogenic differences, each species, N. Langsdorffii and N. Sanderae, being homozygous for one allele each. These alleles have no phenotypic effect in either pure species, but only in hybrids when combined with the genom of N. glauca. The situation is somewhat similar to the sublethal genes reported in interspecific crosses involving N, longiflora (Brieger, 3) and Crepis tectorum (Hollingshead, 8). Since the hybrids with N. glauca are completely sterile, it cannot be decided whether the genes reported are only modifiers or are actually causing the tumour formation and the other abnormalities. 2) A histological study was made about the origin of stem tumours. The first sign is the activation of cells of the tissues between epidermies and collenchyma. Some cells adjoining other which are dead or dying start to grow and later on to divide, in the manner typical for cells under the action of traumatic hormons (cf. Brieger, 2). Later on the whole region is activated and the cortex layers degenerate. At this stage large tumours may be formed, but as yet without connection with the xylem (fig. 15). Later on the cambium and the secundary medulary rays participate in the irregular development (fig. 13) which finally reaches the medulla. Finally the central cylindre is forced open and the tumours connected with it (fig. 14). Thus ...

2 2 (*) Temos usado, em outras publicações, os termos nf 1 e nf2 para indicar os graus de liberdade, mas o emprego destes termos em fórmulas mais complicadas, causa, não somente dificuldade na impressão, mas é ainda, às vezes, a razão de confusões nas fór-mulas, pois o termo nf pode ser interpretado como um produto n vezes f. Assim, estamos usando agora, para o número de variáveis, letras capitais N, M, etc. e as letras minúsculas correspondentes, com ou sem o sufixo f, para os graus de liberdade.