Pollen cells. Sperm cells of Pinophyta and Gnetophyta are without flagella, and are carried by the pollen tube, while those of Cycadophyta and Ginkgophyta have many flagella. When placed on the stigma of a flowering plant, under favorable circumstances, a pollen grain puts forth a pollen tube, which grows down the tissue of the style to the ovary, and makes its way along the placenta, guided by projections or hairs, to the micropyle of an ovule. The nucleus of the tube cell has meanwhile passed into the tube, as does also the generative nucleus, which divides (if it hasn't already) to
Bacillus spore morphogenesis and germination holin family about 90 amino acyl residues in length and exhibit 3 transmembrane segments (TMSs). A representative list of homologous proteins, found only in "Bacillus" species, is available in the Transporter Classification Database. Bacillus spore morphogenesis and germination holin family The "Bacillus" Spore Morphogenesis and Germination Holin (BSH) Family (TC# 1.E.23) is a family of proteins named after a holin in "Bacillus subtilis" described to be involved in spore morphogenesis and germination by Real et al (2005). The gene encoding this holin is "ywcE." Mutants lacking this gene or its product have spores that exhibit outer coat defects. These spores lack the