161 
these buds develop into leafy branches during the same season. It is 
especially to be noted that the lower branches of a tree are often 
still growing after the tips of all the upper branches have 
been cast off. Gleditschia triacanthos (Fig. 6) shows all the 
features just noted of Rodinia The only bud which is visible in 
the axil of the leaves is extra-axillary, being situated a short dis- 
tance above the axil. This bud is cast off as a rule, at an early 
Stage, or on very vigorous branches, develops into a leafy branch 
during the same season. The extra-axillary compound thorn of 
this tree is morphologically equivalent to these buds. As a rule 
the thorns are developed chiefly along the middle portion of each 
year’s growth, but occasionally the thorns occur even at the upper- 
most axils destined to remain. In that case the terminal scar is 
formed just above the last thorn. The visible buds therefore, of 
both Robinia and Gleditschia, (unless they be represented by thorns 
or develop into leaf branches the same season) are cast off. The 
buds which continue the growth of the branch are hidden away 
beneath the petioles of the leaves at this time of the year, so that 
the cast off buds are in reality the uppermost ones of a series of a 
Superposed bud. Gymmnocladus dioica, (Fig. 7) has a roundly angu- 
late terminal scar. The superposed buds are sunken in pits, and 
often drop out. This is especially true of the largest bud in the axil 
of the last remaining leaf, this bud being the uppermost one of its 
series, and hence, lying next to the terminal scar. Cercis Canadensis, 
(Fig. 2) has a little rounded terminal scar. The last remaining 
leaf has a petiole placing itself in line with the stem, as is quite 
commonly the case where the phyllotaxy is alternate and disti- 
chous. A glance at the figures on the accompanying plates will 
readily show this. It is not uncommon to find more than one bud 
even in the last remaining axil, and the larger of these superposed 
buds, the upper one of the series, lies then i Sita the terminal 
Scar. 
Prunus Americana (Fig. 19) shows very distinct terminal scars. 
It is more usual for ligneous Rosacez to have terminal scaly 
buds, so the present exception is worth noting. ae 
Calycanthus floridus (Fig. 25) has well marked terminal sca e 
It was impossible to determine satisfactorily whether Sam- 
bucus Canadensis ever had terminal scars or not. In the . 
