Taxedium 
distichum 
164 ARBORETUM NOTES. 
CONITF ERAS 
CUPRESSINEA. 
general appearance of its foliage, but in a more 
important point. M. Adolphe Brongniart many 
years ago (April, 1857), remarked to me that the 
Conifere of the sub-order cupressee form two 
natural groups, clearly distinguished by the 
arrangement of the leaves.* In cupressus, thua, 
libocedrus (of Endlicher) juniperus, frenela, callitris, 
the leaves are either decussately opposite (that 1s, in 
pairs, crossing each other so that the direction 
of each pair is at right angles to that of the 
next pair above and below), or in verticles of three, 
i.€. in every case either two or three leaves are 
placed on the same level ‘on the branch; 
juniperus, at least, in many of the species, the 
leaves are in pairs, and in threes on different 
branches of the same tree, and even on different 
twigs of the same branch. In taxodiuim sequota, 
cryptomeria, and the remaining genera, the leaves 
are placed in a regularly spiral order, no two 
contiguous ones being on the same _ level. 
M. Brongniart attached much importance to this 
character, and he observed that the scales of the 
cone followed the same law as the leaves, though 
it is not equally apparent. The spiral insertion 
of the leaves in taxodium, is not readily apparent 
in those leaves which are in perfection, on the 
* I believe that he has published this observation, but I do not exactly 
remember where. 
