Varietäten, Descendenz, Hybriden. — Physiologie. 471 



is concluded that, owing to present ignorance of the nature of the 

 variations observed, work on Mendelian lines would probably be 

 economically valueless, though of much importance from the strictly 

 scientific point of view. R. H. Compton (Cambridge). 



Trow, A. H., On the Inheritance of Certain Characters 

 in the Common Groundsel — Seuecio vulgaris, L i n n. — and 

 its Segregates. (Journ. Gen. II. 3. p. 239—276. 4 pl. 4 textfig. 

 1912.) 



The author has cultivated twelve elementary species ot S. vul- 

 garis, and has investigated the mode of inheritance of several of 

 the characters which distinguish them, viz. presence or absence 

 of ray-florets, degree of hairiness, stem- and leaf-colour, colour of 

 corolla, and firabriation of the ray corollas (a new character). All 

 these show Mendelian segregation. The F^ in crosses between radiate 

 and nonradiate forms is intermediate, and F2 consists of the three 

 forras in the ratio 1:2:1. Two factors cooperate in the production 

 of yellow ray-florets: in the absence of both the colour is cream. 

 Redness of stem is a partial dominant to greenness. The inheritance 

 of hairiness is complex: there appear to be a main factor and two 

 "dilution" factors, one acting in radiate plants only; further, coupling 

 is assumed between the hair-factor and the radiate factor on the 

 ratio 2:1:1 :2, and between the hair-factor and the redstem factor 

 on the ratio 1 : n : n : 1 when n is fairly large. Emphasis is laid on 

 the importance of genetical studies to systematics. The author pro- 

 mises further contributions to the subject. 



R. H. Compton (Cambridge). 



Bargagli-Petrucci , G., Alcune esperienze sui movimenti 

 geotropici degli organi immersi nell'acqua. (A proposito 

 dell'esperienza del Giacinto rovesciato). fNuovo Giorn. Bot. 

 XIX. p. 294—308. Taf. XV. 1912.) 



L'experience de la jacinthe renvers^e a donne lieu ä deux inter- 

 prelations differentes: la direction verticale de l'inflorescence plon- 

 gee dans l'eau qui ne se redresse pas sous l'influence du geotro- 

 pisme serait en relation avec la flaccidite des tissus (De Candolle), 

 ou bien avec l'action de la lumi^re qui vient d'en bas, le phototro- 

 pisme devenant la cause determinante de la direction de l'allonge- 

 ment fMaillefer). L'auteur vient proposer une autre explication 

 de ce phenomene; il developpe quelques considerations theoriques 

 sur la theorie des statolithes de Haberlandt, et il decrit des expe- 

 riences montrant la reaction geotropique des organes plonges dans 

 l'eau. Une branche d'ortie fixee sous l'eau par son sommet redresse 

 sa base; fixee au milieu horizontalement sous l'eau eile redresse 

 ses extremites; les anesthesiques, aussi bien que l'eau saturee d'acide 

 carbonique. entravent ou empechent les mouvements geotropiques. 

 Ces experiences expliqueraient selon l'auteur le phenomene de la 

 jacinthe renversee sous l'eau. En raison des alterations dans les 

 echanges de gas et de l'accumulation d'acide carbonique dans les 

 tissus, eile serait dans les memes conditions qu'une branche plong^e 

 dans l'eau saturee d'acide carbonique ou soumise ä l'action des 

 l'anesthesiques; de cette similitude de conditions deriverait un effet 

 semblable, c'est-ä-dire un grand affaiblissement de la faculte de 

 r^agir aux excitations geotropiques. C. Bonaventura (Firenze). 



