1889.] NATURAL SCIENCES OF PHILADELPHIA. 59 



An interesting fact is that at this node, where the terminal growth 

 becomes a supra-axillary raceme, the petiole has assumed a sheath- 

 ins base, and the two lower minute leaf blades are attached to the 

 sheath in such a way that in ordinary cases we should be likely to 

 conclude they were stipules. But we can see that the petiole of the 

 normal leaf has been arrested in its growth, without affecting the 

 laminal portion. It is as if an inch and a half of the normal petiole 

 had been cut out, and a petiolar leaf rendered sessile. With this 

 arrest of growth has come a tendency to dilation, resulting in the 

 sheathing base to the leaf stalk. The observation is important as 

 furnishing the key to other changes as the inflorescence advances 

 in growth. Along the raceme are bracts, from the axils of which 

 the flower springs. These are broad and oval, and in neither form 

 nor texture like the laminal portions of the ordinary leaf. They are 

 evidently formed by a dilation of the petiole, in the line of, and to 

 a greater extent, than in the sheathing condition already noticed. 



The fertilization of the flower is of peculiar interest. Mr. Dar- 

 win treats of Corydalis under the head of self-sterile plants (Cross- 

 and Self-fertilization, chap. 14), though noting there that some 

 species are occasionally self-fertile. This species as growing in my 

 greenhouse, is fully self-fertile — not one flower failing to produce 

 perfect pods and seeds. It is very interesting to observe the de- 

 veloping seed vessel, as it pushes through the maturing petal, car- 

 rying on its up-curved stigma a mass of white pollen, looking like a 

 snow cap on the top of a green mountain. Examining the unopened 

 flowers, we find that the pollen matures, and is actually placed on the 

 stigma, long before the corolla has completed its growth — long before 

 it is in any condition to receive the visits of insects. It is in fact as 

 truly fertilized in the bud, as that class of apetalous conditions 

 known as cleistogene flowers can possibly be. This can be readily 

 understood by observing that in a raceme of ten flowers, the lower 

 one only with the pistil having emerged from the closed flower, all 

 but the two upper had pollen on their stigmas. It is a case in which 

 the flowers are arranged for self-fertilization, with perfect productive 

 results. 



Dimorphism in Polygona. " Flores hermaphrodite," is said of 

 the whole section of Polygonacece in which Polygonum is included ; 

 but though hermaphrodite they be, the hermaphrodism, so far as an 

 examination of species growing near the author is concerned, is of a 

 character hitherto unsuspected by botanists. 



