18 Morphologie etc. — Varietäten etc. 



Zählungen, dazu die von ihm selbst vorgenommenen. Beide Arbei- 

 ten würden wohl interessante Resultate geben, wenn man die 

 Zählungen phylogenetisch verwerten würde. Die meisten Vio- 

 laceen können jetzt schon in eine Reihe mit 6, 12, 24, 36 Chromo- 

 somen geordnet werden, da es nur 4 Ausnahmen gibt. Dies gilt 

 aber nicht für die Compositae] so haben die Heliantheen nicht, wie 

 Winge angibt, 8 oder ein Vielfaches von 8 an Chromosomen, 

 sondern nach Verf. 18 {Xanthium), 15 {Wedelia), 12 {Zinnia), 17 

 {Helianthtis). Bei Lactuca fand Verf. gar die Zahlen 5, 8, 7, 9, 12, 

 11, 24. Da heisst es also mit Vorsicht weitgehendere Schlüsse 

 ziehen. Matouschek (Wien). 



Benedict, R. C, The origin ofnew varieties ofNephrole- 

 pis by orthogenetic saltation. I. Progressive Varia- 

 tion s. (Bull. Torrey Bot. Club. XLIII. p. 207-234. PI. 10-15. 1916.) 



The Contents of the paper are summarized by the author as 

 follows : 



Nephvolepis, a genus of once-pinnate tropical ferns, includes 

 several species which are cultivated. Nearly all of these cultivated 

 species show Variation by bud sports, but N. exaltata through its 

 variety bostoniensis is most prolific, having given rise to more than 

 one hundred different forms in less than fifteen years. 



Cultural conditions are such as to favor the appearance and 

 preservation of variations, because the soil and other environmental 

 conditions are probably practically perfect, and because ver}' iarge 

 numbers of plants, one to two million, are grown per annum in the 

 United States alone. 



The variations may be classified under two headings, progres- 

 sive, and regressive or reversive. Progressive varieties are defined 

 as those which show less resemblance to var. bostoniensis than 

 their parent forms. Regressive variations are defined as those which 

 show something of a return in characters toward var. bostoniensis. 



Progressive variations have appeared along three main lines, 

 viz., those showing increased division of the leaf; those showing 

 increased ruffling of the pinnae; those showing dwarfing. Variations 

 showing dichotomy of the pinnae and leaf tips also occur. 



Progressive increase in division has gone through five vegeta- 

 tive generations, each succeeding step being an intensification of 

 the preceding, the forms varying from once to five times pinnate. 

 Progressive increase in ruffling has gone through three vegetative 

 generations. Progressive dwarfing has gone through three vegetative 

 generations. 



The dwarfing seems to be clearly of two sorts: first, brachyotic 

 or unilear; and second, normal in all dimensions. More than one 

 type of division sport is also indicated. 



Progressive increase in leaf division and progressive dwarfing 

 may be expected in any form which has not reached the limits of 

 Variation along these lines. 



Regressive variations rarely if ever show complete return to 

 their parent forms or to var. bostoniensis. 



The indicated cocfficient of Variation for progressive variations 

 is very low; probably between one in one million and one in one 

 thousand. Regressive Variation is much more common. 



The variations are all discrete or discontinuous, not proceeding 

 by imperceptible differences. 



