116 Varietäten, Descendenz, Hybriden. 



Baart de la Faille, C. J., On the logarithmic frequency 

 curve and its biological importance. (Recueil des Trav. 

 bot. Neerl. XII. p. 349—368. 1915.) 



The use of logarithmic curves in Variation statistics seems 

 never to have been tried earnestly; a gap remained therefore to 

 be fiUed up. Feeling a favourable disposition towards this curve 

 because of the simplicity of its basis, the author of this paper has 

 been looking for instances and found them among his extensive 

 measurings of a material, which he had collected for his disserta- 

 tion, namely 300 plants of Senecio vulgaris L. For most of the cha- 

 racters the author had taken only one measure per plant, but a 

 few series were i-epresented by more measures, and among these 

 were the two instances which are described in this paper, viz. the 

 top cells of pappus and the short bracts of the involucre. 



From the first series of measurements (2750 top cells of pappus, 

 collected on 275 plants) the author draws this conclusion: „1 con- 

 clude almost vt'ith certainty, that, in the case of my pappus cells, 

 the logarithmic curve is the true one, so that the grov^rth of these 

 cells has been governed by this law: Increase directly proportional 

 to the length already acquired." 



And from the second series the conclusion runs as foUows: 



100 

 „About --— =r 93°/q of the bracts in question belonged to a type 



governed fully by the Law of the Geometrie Mean. The remaining 

 70/q (in this case about 241) were nontypical, transitional leaflets, 

 some inserted lower and the rest higher, but all of greater length." 

 It is the writers personal conviction, that logarithmic distribution 

 represenls a more frequent case in nature than even the Normal 

 curve. Among 145 frequency series from his own material no less 

 than 111 showed positive skewness; the predominance of positive 

 skewness is considered as a very strong indication of a more fre- 

 quent occurrence of logarithmic distribution than has hitherto been 

 supposed. M. J. Sirks (Bunnik). 



Cohen Stuart, C. P., Voorbereidende onderzoekingen 

 ten dienste van de selektie der theeplant. [Recher- 

 ches preliminaires au Service de la selection du 

 theierj. (Med. Proefst. Thee. Buitenzorg. XL. 328 pp. 2 cartes 

 geograph. 3 pl. 53 fig. et diagr. 1916. — en meme temps thfese de 

 doctorat Utrecht.) 



Dans cet ouvrage-ci l'auteur, assistant ä la Station d'essai pour 

 la culture du the ä Buitenzorg, publie les resultats obtenus de 

 son travail pendant son sejour de 2 ans ä Buitenzorg. M. Cohen 

 Stuart a la modestie de presenter son travail comme „recherches 

 preliminaires", bien que l'ouvrage doive etre plutöt pris comme 

 monographie. 



Le Premier chapitre du livre renferme un apergu historique- 

 geographique de l'origine et de la distribution ä travers les parties 

 du monde du theier comme matiere de culture primitive. La con- 

 naissance du theier avant 1825 etait confuse au plus haut degre: 

 on ne saurait plus identifier les divers noms scientifiques, fondös 

 par Thunberg, Alton, Salisbury et Loureiro, avec aucune 

 plante et c'est pour cela qu'on doit les considerer comme inutiles 

 ä present. Meme l'ancienne maniere de distinguer le the noir du 

 the vert ne peut plus servir comme moyen de distinction dans la 



