NOTES. 
THE DELAYED DEHISCENCE OF CALLXSTEMON RIGID A, R. BR.~ 
This plant, commonly known as the stiff or rigid Bottle Brush, first described by 
R. Brown in the Botanical Register , 1819, PI. 393, is frequently grown in Mel- 
bourne, although a native originally of West Australia. The tufts of red flowers 
at the ends of the branches are very striking in appearance, and leave behind sessile 
closely-set fruits which ultimately dehisce by three oval apertures in the centre of the 
flattened top of the semi-succulent fruit. 
Since the plant flowers each year at the ends of the youngest branches only, the 
age of the fruit is that of the branch bearing them. Each fruit, sessile on the bark, 
is connected by a short stalk to the wood-cylinder of the year of its formation, the 
clusters of fruits leaving the wood perforated at such points by knot-holes. Hence 
the age of a fruit can be further verified by counting the number of annual rings 
inwards to the point of origin of its stalk. 
When first formed the fruits are separated by spaces from one another, but since 
they grow at first relatively more rapidly in diameter than do the branches, they come 
into very close contact and remain so for the first two or three years. Ultimately 
they separate again, owing to the branch steadily increasing in diameter, while the 
fruits have practically ceased to grow. The same applies to the knots in the wood, 
which, after the fruits have fallen, are soon obliterated in the succeeding year's 
growths of wood. The fruits normally persist on the plant for many years, finally 
becoming rough and corky on the surface, though still containing living pericarp- 
cells, the pericarp-tissue being watery and pale green, with few scattered chloro- 
plastids, more distinct in the younger fruits. These have no special cambial tissue 
except on the surface, where the layers of cork are formed, and on the stalk, where 
the latter passes through the cambium of the stem. The fruits nearly cease to grow 
in their second year (o-8 to 1 cm. diam.), the total increase in the next ten or even 
eighteen years being not more than 1 to 2 mm. The edges of the semi-succulent 
receptacle, however, which are at first nearly flat with the three carpellary valves, grow 
a millimetre or two upwards and inwards over the valves, sometimes nearly closing 
these in, but on drying always contracting so as to allow their dehiscence to set 
free the seeds. 
Dehiscence and the escape of the seeds is normally delayed for three, four, or 
more years, and in one case portions of a cluster twenty years old were undehisced ; 
the pericarp contained living and plasmolysable cells, and of the small linear seeds 
many also were found on microscopic examination to contain undoubted living cells. 
In the dry air of the laboratory, the fruits dehisced on cut branches, and the minute 
brown seeds fell in quantity. The same occurs in the open if an attached branch is 
[Annals of Botany, Vol. XXI, No. LXXXI. January, 1907,3 
