138 



The Plant World 



and more or less pinnatifid and spiny, and since the two are close- 

 ly related genera it might be suspected that this new form is a 

 hybrid between some species of Carduus and Arctium minus. 

 But it seems rather improbable that cross pollination could be 

 effected between plants of this type. Then, too, the preponder- 

 ance of Arctium characters is against such a conclusion. 



Is the plant a monstrosity or a mutant that has originated 

 among the progeny of Arctium minus? This seems to me to be 

 the most probable explanation. Minus is the only species of 

 Arctium growing in the locality mentioned. Such aberrant 

 forms have been known to appear among the progeny of different 

 species of plants and when they breed true they are known as 

 mutants. The oldest mutant on record is that of Chelidomum 

 laciniatum, a laciniate-leaved form which sprang from Chelid- 

 onium majus at Heidelberg in 1590. Other species and varieties 

 have arisen in a similar way from time to time. The parent 

 species is usually regarded as being unstable or progressive. 

 Can it be that the well-defined genus Arctium, with its few 

 species is becoming unstable and is beginning to throw off 

 mutants? Notes on observations made in different places will 

 be gladly received. 



Cornell Un ivers it) 1 . 



BOOKS AND CURRENT LITERATURE. 

 Edward C. Jeffrey, in the March, 1909, number of Rhodora, 

 contributes an important article On the Nature of So-called Algal 

 or Bog-head Coals. In preparation of material for microscopic 

 examination, hydrochloric acid was replaced by hydrofluoric 

 acid, followed by careful washing of the coals and soaking in hot 

 alcohol containing from three to five per cent of alkali. By this 

 means the coal is softened without disorganization and may be 

 successfully sectioned. In the study of certain bituminous coals 

 known as Bogheads, Dr. Jeffrey has been able to demonstrate 

 that the supposed algae of Renault and Bertrand are, in reality, 

 "large spores or macrospores of vascular cryptograms which 

 flourished during the coal periods, the imagined algae being, in 

 fact, only the pores in the strongly sculptured coats of these 

 spores."' As the result of his observation it appears probable that 



