FORMATION OF TUBES. Si 
attached to the inner surface of the corolla; sometimes 
these petaloid tubes replace the stamens, while at other 

Fra. 168.—Corolla of Primula sinensis turned back to show a tubular 
petal springing from it. One only is shown for the sake of clearness ; 
they are generally numerous. 
times they appear to haye no relation to those organs. 
In the particular flowers now alluded to the tubular 
form seems due to a dilatation, and not to a cohesion 
of the margins. (See Cohesion, p. 23.) These tubular 
petals resemble in form and colour almost precisely the 
normal corolla in miniature, but are not surrounded by 
a calyx, nor do they contain stamens, while the less 
perfect forms show clearly their origin from a single 
tube-like organ. 
The formation of spurs or spur-like tubes in a quasi- 
regular manner has been spoken of under the head of 
Irregular Peloria, p. 228, but we occasionally meet 
with tubular processes which seem to occur in an 
irregular manner, and to have no reference to the 
symmetrical plan of the flower, and which are due pro- 
bably to the same causes as those which induce hyper- 
trophy. Such spurs have frequently been seen on the 
corolla of Digitalis purpurea, Antirrhinum majus,' 
Tulipa Gesneriana, and occasionally on the sepals of 
' Chavannes, ‘ Mon. Antirrh.’ 
