313 
buds, as those of the horse chesnut, are coated with a resinous varnish; others* 
as the buds of the willow, are protected with a thick, downy covering. la 
tropical climates, where the temperature is not hurtful to the young bud, no 
such elaborate protection is needed, and in most cases none is provided. 
Leaves are most important organs, and their structure and functions should 
be clearly understood by all cultivators of plants. A leaf is a continuation of 
the bark; the veins consist of vascular tissue; the spaces between the veins be¬ 
ing filled up with cellular parenchyma. There are at least two setts of vein?,, 
as may be seen in skeleton leaves obtained by macerating leaves in water. Tho 
upper strata communicate with the medullary sheath of the wood, and contain 
spiral vessels and woody fibres. The low 7 er strata is in connection with tho 
bark, aud consists of laticiferous and other vessels resembling those of the liber 
or inner bark. Leaves are commonly arranged on the stem in a spiral manner 
which enables them adequately to perform their functions, by exposing all alike, 
to the action of light. The leaves of exogens are commonly arranged in cycles 
of five. If we take a freely developed branch of the apple or cherry, for in¬ 
stance, and pass a thread round the stem from leaf to leaf; when we reach thei 
sixth we shall have made two spirals, and find that the sixth leaf is directly over 
the first, the seventh over the second, and the eleventh over the first and sixtlu 
The reproductive organs—the flower and fruit—are now considered to be 
leaf formations, variously modified to serve special purposes. A flower usually 
consists of four parts—1. the calyx; 2. the corolla; 3. the stamens; and 4. tho- 
pistil. The floral envelopes, calyx and corolla, are generally easily distinguished 
from each other in exogens. The calyx is on the outside, and usually green,, 
while the corolla is mostly highly colored. In some plants there is only one- 
whorl developed, and it is then considered to be the calyx, although it may be 
colored. The essential organs are the stamens and pistil. The stamens usually 
consist of two parts, the filament and the anther. These constitute the male 
apparatus of plants. The anther is a cellular case, whieh, when perfect, opens and 
discharges the pollen, a dustdike substance, by means of which the fertilization? 
of the embryo seeds is accomplished. The pistil occupies the centre of the 
flower, and consists of one or more carpels or seed-vessels. The pistil may be 
divided into three parts, the ovary, the style, aud the stigma. The ovary is the 
case containing the embryo seeds or ovules. The style is the part which coe- 
nects the ovary with the stigma; it is not essential, and is sometimes absent 
The stigma is generally the summit of the pistil. It is the part which receives. 
