Biologie. — Descendenz und Hybriden. 661 



waren Scapanla nemorosa und irrigua, Jungermannia albicans, 

 J. i/iflata, Lophocolea bidentata, L. minor, Lepidozia reptans, 

 während Ptilidium ciliare immer nur äusserlich von Hyphen 

 umsponnen war. Von den auf der Erde wachsenden thallosen 

 Jungermanniaceen besitzen Aneura multifida sehr wenig, Pellia 

 epiphylla meist verpilzte Rhizoiden ohne jedoch dichte Hyphen- 

 knäuel zu zeigen. Bei den baumbewohnenden Metzgeria furcata, 

 Radula complanata, Frullania dilatata und Madotheca platy- 

 phylla sind die häufig verschleimenden Rhizoiden mehr 

 Haftorgane und die Hypheninfection ist sehr unregelmässig. — 

 Von der schon seit langem bekannten (Ruy 1873) Marchantia- 

 Mycorrhiza wird ihre Inconstanz hervorgehoben. — Das All- 

 gemeinergebniss ist, dass die Mycorrhiza der Lebermoose durch- 

 aus nicht etwas so constantes und einförmiges ist, wie die 

 Mycorrhiza vieler höheren Pflanzen und dass die ganze Er- 

 scheinung einen mehr parasitären Charakter hat. 



Werner Magnus (Berlin). 



BäTESON, W., Note on the Resolution of Compound 

 Characters by Cross-breeding. (Proc. Cambridge 

 Philosophical Society. Vol. XII. Parti. 1903. p. 50— 54.) 



The author endeavours to modify Mendel's theory of 

 colour-inheritance, so as to simplify the conception of what 

 occurs in such cases as that recorded by de Vries (Mu- 

 tationstheo rie, II. p. 196) in which a red-flowered Antir- 

 rhinum was crossed with a white-flowered form. The result 

 of the cross was a series of red-flowered plants, so that white 

 was „recessive". The hybrids, when self-fertilised, gave plants 

 with flowers of one of four types, red, flesh-coloured, „Delila" 

 (the tube pink or white, the ups red), or pure white. These 

 four kinds of plants occurred with a relative frequency regarded 

 as an approximation to 9:3:3:1. De Vries, following 

 Mendel, regards this result as evidence that the original red 

 is due to two gametic units, one giving flesh-colour, the other 

 „Delila", each dominant over white, and in order to meet this 

 condition of the red parent, the colour of the white parent is 

 assumed to be determined by two gametic units, of identical 

 character, an assumption already made by Mendel for Pha- 

 seollis. The results of the cross may therefore be written. 

 (W + W) X (D -f F) = (WD + WF). 



Bateson objects that the double nature of the white 

 unit is purely hypothetical, and endeavours to avoid such 

 hypothetical complication. He assumes that the original red 

 race is determined by three elements, red (R), flesh-colour (F) 

 and „Delila" (D). It is stated that experimentally R is domi- 

 nant to D, and that F X D gi ve rec ^- Now, when the hybrids, 

 produced by pairing the original red-flowered race with a white- 

 flowered race, form their gametes, Bateson suggests that the 

 gametes of each sex are of four kinds, each equally frequent, 

 and each containing one only of the elements R, D, F or W 



