318 PROCEEDINGS OF THE ACADEMY OF [April, 



terminal odd leaflet. Several steps in this suppression of the odd 

 leaflet were gathered. One pinnate foliage leaf shows a very 

 narrow somewhat unequally trilobed odd leaflet; another a still 

 narrower almost linear, glandular-toothed terminal leaflet. A 

 third one has a filiform odd leaflet; a fourth pinnate foliage leaf 

 has a simple boss in place of the odd leaflet, this small protuber- 

 ance seeming to persist as a rudiment in all of the leaves studied. 

 This arrestment of the normal development is carried a step far- 

 ther, the terminal paired lateral leaflets beginning to manifest a 

 reduction in size, becoming in one leaf studied small, elliptical in 

 outline with a retuse apex, all the other leaflets studied having an 

 acuminate apex. The other line of variation stai-ts with the 

 lanceolate odd leaflet which becomes increasingly broader. Some 

 have a rounded, retuse apex, others have an acuminate point. 

 From simple glandular teeth at the base of the odd leaflet, these 

 glandular teeth increase in size until they become glandular tipped 

 lobes separated from each other by rather shallow, acute sinuses, 

 this line of advanced development proceeding until the terminal 

 leaflet reaches a broadly ovate, trilobed form, each lobe being 

 narrowly acuminate. Finally, as if to approach a climax, one of 

 these lobes becomes almost distinct at the base, but is still concres- 

 cent with the basal part of the leaflet and the upper side of its 

 petiole. In another leaf gathered, as representing the climax, 

 this lanceolate entire basal lobe is separated by the cutting in of 

 the sinus to the midrib; the asymmetric upper portion also becomes 

 deeply lobed by the formation of rounded depressions. The lateral 

 intermediate leaflets of the pinnate leaves are all asymmetric with 

 an oblique base, the obliquity inclining downward. A glandular 

 tooth is usually found on the upper and lower margins; if three 

 glands are present, two are found on the lower margin, oue^on the 

 upper. If only one gland is present it is always on the rounded, 

 oblique lower edge. Occasionally a basal, rounded, glandular- 

 tipped lobe is found on the lower edge of the lateral pinuie of a 

 large foliage leaf. We cannot doubt that asymmetry of leaflets 

 chiefly appears when their parts are unsymmetrically related to 

 their environment."' We may say in general, with Herbert Spen- 

 cer, that that side of the leaf is the smaller which is shaded, and 



^^ Herbert Spencer, Principles of Biology, II, p. 113. 



