III. BOTANY AND ZOOLOGY. 



1. Dimorphism in the Genitalia of Flowers. — Two principal kinds of 

 this diinorpliism have been noticed in a great number of instances, and 



and systematized, nor liad the import of the most curious case been made 



dimorpliism which Mr. Darwin has recently illustrated in his paper "On 

 the two forms, or Dimorphic Condition, in the species oi Primiih:' which 

 was briefly noticed in the preceding number of this Journal (p. 285). 

 This was 'here long ago named dio-xio-dimorphism (see Flora N. Amer- 



iiuderstood, for these blossoms altliough hermaphrodite structurally are 

 functionally as if dioecious, or nearly so, the end subserved being fertili- 

 zation of the ovules of one flower by the pollen of another flower on 

 another individual. 



The diceeio-dimorphous species o( Flantago had seemed to confuse this 

 case with the next. That is, the short-stamened flowers appeared to be 

 fertilized in the closed flower, and the longstamened and generally ster- 

 ile plants therefore to be generally useless. This could hardly be; and a 

 recent observation on a single specimen (likely to be confirmed in others) 

 shows the top of the style projecting from the tip of the closed corolla. 

 This refers the case to the same category with Houstonia, Primula, &c., 

 to which P. prisella and P. heterophylla, having the corollas of the short- 

 stamened form open in anthers, and the stigma projecting, evidently be- 

 long. It is to be noted that dimorphism, both of this and of the follow- 

 ing''sort, is apt to be variable either in mode or in degree in different 



of a genus, some of°thera being unaffected, while others in some genera 

 are nt;arly 'polygamous or dioecious ;— which is all very favorable to the 



The second case, which equally belongs to structurally hermaplirodite 

 flowers, is practically the reverse of the first. It is the case in which, 

 besides' the normal flowers of the species, which for the most part are 

 rarely or sparingly fertile, other flowers are produced which never open, 



very prolific of seed. Here the stigma is, and must needs be, fertilized 

 by "pollen from the anthers of the same flower, the two bemg shut up 

 together in the same closed bud. The acaulescent Violets and the com- 

 mon wild species of Impatiens are good exaniples of the kind. In fact, 

 here impregnation is etiected as it were in th.3 early bud ;-wherefore we 

 had indicatt^d these as cases of precocious fertilization. Here the pollen is 

 unusually active, sending out its tubes while still in the anther, and 

 thereby in Impatiens, (fee, attaching the anthers to the stigma. In the 

 viduaTof^hripecS: Sl'the oTher, onTe'contrary, she takes equal pains 

 to secure self-fertilization. The end in the first case, as Mr. Darwm mam- 

 tains, (we believe upon good philosophical grounds, now m the course of 

 vindication by experiment) is to ensure the perpetuation of the species, 

 Am. Joua. Sci.-Second Series, Vol. XXXIV, No. I02.-Nov.. 1863. 



