— 50 — 



portion of catkin. The portion of bract is generally coloured and 

 pubescent. The upper part of bract-like scale whei'e refiexing is 

 always blackish or reddish in colour. This coloured part and the dorsal 

 side correspond to the bract, both are usually pubescent. On the other 

 hand, the inner surface of scale near its base, being creamy in shade 

 and glabrous, is the outer perianth corresponding to the cupule of 

 Populus. When this portion ill developed, the bract is very thin ; 

 sometimes the scale is made of the entire bract toward its base. In 

 such case, the scale is deciduous (for examples : Sect. Pentandros and 

 Urbaniance, or Phygalilepideos of Trautvetter). The horizontal 

 furrows on the dorsal side of the scale are the result of unequal 

 development of bract and perianth. If one imagines that the perianth 

 of Populus much reduced its height, he can easily compare the relation 

 of perianth and bract with the fused scale of Salix. 



Next, the degeneration of flowers of Salix is to be traced. In 

 geological epoch, the ancestors of Salix are supposed to have had 

 polygamous flowers with many indefinite stamens. However, many 

 of stamens diminished and gradually became as 20 — > 15 —■ * 10 — > 6 or 

 5, and where the stamens reduced to 6 or 5 is a starting point of the 

 degenerated flowers of present Salix. Mrs. J. Fischer has almost come 

 to the similar conclusion in this respect (see Flowers of Salicacece in 

 American Journal of Botany XV, 1928). The imaginary diagrams of 

 complete hermaphrodite flowers of Salix with 6 or 5 petals are shown 

 in the text-figure A. If in figure A, the ovaries united into one, the 

 floral diagram would become like the text-figure B. Then, the 

 adherence of bract and perianth, degeneration of ovaries and their 

 disappearance in male flowers, metamorphosis of the inner perianth 

 to the nectaries, the reductions of nectaries and stamens have succes- 

 sively followed. Each stage in the reductions is illustrated by the 

 floral diagrams from the text-figure C to the text-figure J. 



In polyandrous flowers, number of stamens fluctuates between 10 

 and 20, but in this it is generally indefinite (text figure K). 



In 6-stamened flowers of Salix glandulosa, it will be seen that two 



