SHOOTS 
73 
leaves that no peculiar stem type is developed. In the 
pines scale leaves are found abundantly on the stems which 
are developed for foliage purposes. In fact, the main stem 
axes of pines bear only scale leaves, while short spur-like 
branches bear the characteristic needles, or foliage leaves, 
but the form of the 
stem is controlled 
by the needs of the 
foliage. Some very 
distinct types of 
scale-bearing stems 
may be noted. 
50. The bud type. 
In this case the 
nodes bearing the 
leaves remain close 
together, not sepa- 
rating, as is neces- 
sary in ordinary 
foliage-bearing 
stems, and the 
leaves overlap. In 
a stem of this char- 
acter the later joints 
may become sepa- 
rated and bear foli- 
age leaves, so that 
one finds scale leaves below and foliage leaves above on 
the same stem axis. This is always true in the case of 
branch buds, in which the scale leaves serve the purpose 
of protection, and are aerial, not because they need a 
light-relation, but because they are protecting young foli- 
age leaves which do. 
Sometimes the scale leaves of this bud type of stem do 
not serve so much for protection as for food storage, and 
become fleshy. Ordinary bulbs, such as those of lilies, etc., 
FIG. 63a. Cotyledons of castor-oil bean ; the seedling 
to the left showing the ordinary position of the 
cotyledons, the one to the right showing the curva- 
ture of the stem in response to light from one 
side. After ATKINSON. 
