Notes. 
596 
The rate of cambial activity is of especial value in determining the 
varying significance of the xylem differentiations in slow-growing 
deciduous or quick-growing evergreen trees. 
HERBERT WRIGHT. 
Peradeniya. 
THE MORPHOLOGY OF SPORANGIAL INTEGUMENTS 1 . 
Angiosperms. 
Theories on the nature of the integuments of the ovule : — 
1. Foliar-appendage theory : The integuments are the foliar ap- 
pendages of the nucellus, which is a stem structure. Supporters of 
this view : Alex. Braun, Aug. St. Hilaire, Schleiden, Payer, Schmitz. 
2. Sui generis theory : The integuments are special protective out- 
growths of 'the sporangium, this latter being an organ sui generis. 
Evidence for this view is afforded solely by facts of ontogeny : Stras- 
burger, Goebel, Eichler. 
3. Foliolar theory : chiefly elaborated by last of undermentioned 
authors. Based entirely on the evidence of the abnormal metamor- 
phoses of the ovule ; these are of a very constant character, subject to 
control of very definite laws ; the two integuments tend to proliferate 
into a three-lobed marginal leaflet or segment of the carpel, of which 
the terminal lobe, bearing the nucellus (when present) on its upper 
surface, represents the inner, while the two lateral lobes represent the 
outer integument ; this is the extreme proliferated form. Between this 
and the normal ovule every intermediate transitional form has been 
observed , the extent of proliferation depending on the stage of develop- 
ment of ovule at which the tendency thereto sets in. Cases where pro- 
liferated outer integument appears as a simple lamina bearing normal 
cup-shaped inner integument containing nucellus on its lower surface ; 
this structure arises morphologically by fusion of the inner margins of 
the two lateral lobes of the leaflet in the extreme proliferated form 
across the face of the latter, the terminal lobe at the same time becoming 
inrolled. The whole structure and mutual relationship of the parts is 
well shown by means of certain abnormal forms of foliage-leaf in 
Syringa. Hence the ovular integuments are the morphological homo- 
1 Abstract of paper read before Section K of the British Association, Belfast, 
1902. 
