PKEFACE TO THE SECOND EDITIOK 



Since the publieatioii of the first edition of this 

 book in 1877, several articles have appeared on the sub- 

 jects therein discussed, and many letters have been re- 

 ceived by me. I will here briefly state their nature, 

 as an aid to any one who may afterwards pursue the 

 same subjects. The text has been left as it originally 

 appeared, excepting that a few errors have been cor- 

 rected. 



Dr. A. Ernst has proved in the clearest manner 

 '('Fature,' Jan. 1, 1880, p. 317) that Melochia parvi- 

 folia, which is a common plant near Caracas, is hetero- 

 styled. The pollen-grains differ in the usual manner 

 in size in the two forms, as do the papillae on their stig- 

 mas. The illegitimate unions, especially when pollen 

 from the same flower was employed, were much less fer- 

 tile than the legitimate ones. A new family, the Bytt- 

 neriacese, is thus added to those including heterostyled 

 plants. 



Errara and Gevaert have published a paper on the 

 heterostylism of Primula elatior, in ' Bull. Soc. E. Bot. 

 Belg.,' torn, xvii., 1879. 



I have quoted (p. 100) Dr. Alefeld's statement that 

 none of the American species of Linum are heterostyled. 

 This statement was disputed by Kuhn ('Bot. Zeit.,' 

 18C6, p. 201), but has since been confirmed by Dr. Ign, 



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