34 
BULLETIN OF THE LABORATORIES 
D. Irregular Superposition. 
I. Sympodial Growth, — Those species of plants, especially 
common among Solanaceae, in which an axillary branch continues the 
stem of the plant while another bud is formed in the axil of its sub- 
tending leaf, have often been made the subject of special investigation 
and can be studied in books especially devoted to this subject. The 
Vitaceac among ligneous plants present cases in some respects similar 
to these. They are all caused by sympodial growth. 
II. Zig-zag Superposition. — Scarcely any other term will express 
the arrangement of the superposed branches and buds of the plants 
in question. In Thalictriim dioicum the branches will be found 
thrown alternately towards the right and left of a true median line. 
The superposed buds, both leaf- and flower-buds, of Aristolochia 
Clematitis will be found arranged in a similar manner. Atriplex 
patula shows the same manner of arrangement. (See Eichler, Blue- 
thendiagramme, 11 . , pp. 83, 533 and 159.) Various species of Leg- 
uminosae present the same or similar features. In their case the in- 
terest is so much greater, on account of the ordinary forms of super- 
position common to both the ligneous and herbaceous plants of this 
order. Thus, for example, in Melilotus alba the buds are thrown al- 
ternately towards the right or left of a true median line, and even 
where only two buds are found and where crowding is not so evident 
the same features still present themselves. In closely related species 
of Trifoliimi^ however, the. superposition is of the ordinary kind. 
II. DIRECT SUPERPOSITION. 
Lonicera Tartarica (7). Two to five buds are here superposed. 
The one directly in the axil is formed first, and those above at success- 
ively later periods. The lowest bud is the strongest and generally 
produces the branch, but occasionally several of them develop. Among 
flowering branches, the lowest buds produce the flowers, or flower- 
clusters. Coreopsis tmctoria (16). — The upper leaf axils contain a 
flowering branch, superposed to which is a small bud which later in the 
season produces two or three leaves and a flower. C. tripteris has 
larger and more developed superposed buds, the upper of which bears 
leaves and two or three flowers. The superposed branch is inserted, 
as in the first, directly between the axillary branch and the stem. 
Fassiflora lutea. — Immediately in the axil is a tendril which represents 
