1906] SHREVE—SARRACENIA PURPUREA 113 
_ tissue, and in some preparations the antipodals would seem to have 
been pushed to one side (fig. 27). The columnar layer now shows 
its maximum development, being made up of deep, much-flattened 
_ cells with darkly staining cytoplasm. The function of these cells 
is no doubt that of secreting and passing over to the sac sugars or 
other elaborated foodstuffs. 
POLLINATION AND POLLEN TUBES. 
Pollination takes place, near Baltimore, during the first week in 
May. In the mature style of Sarracenia at the time of pollination 
the umbrella is a pale green color. Its internal structure is leaf-like 
_ without a definite palisade, but with abundant intercellular spaces 
4 and stomata numerous upon the upper surface and few upon the 
4 lower. Long unbranched unicellular hairs cover the lower surface 
_ so thickly as to form a tomentum in which considerable pollen is 
caught at the time of shedding. There are also upon both sides of 
the umbrella multicellular glands of spheroidal shape projecting 
slightly above the level of the epidermis. Running from the five 
stigmatic surfaces toward the center of the umbrella are heavy veins 
~ which comprise both vascular and conducting tissue. 
_ The union of the carpels in the formation of the stalk of the 
style is such as to leave at its center a pentagonal cavity which in the 
mature flower connects the interior of the capsule with the external 
air. An cxamination of the veins of the umbrella two weeks before 
pollination will show the conducting tissue as a cylindrical strand 
about ten cells in diameter. The cells are much elongated, with 
pointed ends, or many cells of this description have divided trans- 
versely to two or four cells. The cytoplasm is dense, the nuclei are 
large, elongated, often three times as wide as long, binucleolate, and 
poor in chromatin. At the time of the passage of the pollen tubes 
the conducting strand has become enlarged to more than twice its 
_ previous diameter at the expense of the surrounding tissue, and the 
cells have become still more elongated. The cytoplasm is much vacu- 
-Olated, the nuclei are attenuate at the ends and devoid of nucleoli 
(78s. 32, 33), and there are large intercellular spaces. The vascular 
tissue of the veins lies beneath the conducting tissue and is continuous 
‘ with the vascular tissue of the stylar stalk. 
