. Morphology of gymnosperms. Gymnosperms; Plant morphology. CONIFERALES (TAXACEAE) 345 taxus Fortunei (124), and PhyUocladus (144) the functioning male cell, with its complete investment of cytoplasm, has been observed to come in contact vs^ith the egg nucleus (figs. 399, 400). In this position, the male cytoplasm spreads from its own nucleus and invests the egg nucleus, and this investment is very evident in the fusion nucleus, and may persist in Torreya taxifolia as a distinct cytoplasmic sheath even about the four free nuclei at wall-formation. This sheath is recognizable on account of its
. Morphology of gymnosperms. Gymnosperms; Plant morphology. CONIFERALES (TAXACEAE) 345 taxus Fortunei (124), and PhyUocladus (144) the functioning male cell, with its complete investment of cytoplasm, has been observed to come in contact vs^ith the egg nucleus (figs. 399, 400). In this position, the male cytoplasm spreads from its own nucleus and invests the egg nucleus, and this investment is very evident in the fusion nucleus, and may persist in Torreya taxifolia as a distinct cytoplasmic sheath even about the four free nuclei at wall-formation. This sheath is recognizable on account of its abundant supply of food material, and is doubdess of serv- ice in the nutrition of the fusion nucleus. ' In Cephalotaxus drupacea (130), in which male cells are not formed, the two free male nuclei do not escape from the mem- brane of the body cell until at the time of dis- charge. An interesting conse- quence of the early ap- pearance and fertilization of the eggs of Torreya taxifolia may be men- tioned. At this time the endosperm tissue has not grown, and in its subsequent development it grows about the tip of the pollen tube, incloses the fertilized egg, and forms quite a beak above the embryo. Critical observations of fertilization among the conifers are not numerous enough to form the basis of a general conclusion, but the evidence thus far indicates that the behavior of the male cytoplasm, in investing the fusion nucleus as a nutritive zone, is a feature of the •Taxaceae; while among the Pinaceae the male nucleus slips from its cytoplasmic sheath in the periphery of the egg cytoplasm (with Taxo- dium and Juniperus as exceptions). Subsequent investigation may show that both methods belong indiscriminately to both Fig. 400.—PhyUocladus alpina: fertilization; both male cells are shown, the one at the right is functional, and the one at the left is disorganizing; X440.—After Miss Young (174).. Please note that these images are extracted from scanned page imag
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