. A manual of the North American gymnosperms [microform] : exclusive of the cycadales but together with certain exotic species. Bois; Trees; Gymnosperms; Gymnospermes; Arbres; Wood. BORDERED PITS 67 © ©. This IS undoubtedly a primitive character, and in the one case cited It possesses some value for the purpose of specific differ- entiation, but in general terms the occurrence of bordered pits in such positions is of so sporadic a nature as to give this feature no well-defined value, either for taxonomic or phylogenetic purposes! It may, nevertheless, be stated with respect to the pits on the
. A manual of the North American gymnosperms [microform] : exclusive of the cycadales but together with certain exotic species. Bois; Trees; Gymnosperms; Gymnospermes; Arbres; Wood. BORDERED PITS 67 © ©. This IS undoubtedly a primitive character, and in the one case cited It possesses some value for the purpose of specific differ- entiation, but in general terms the occurrence of bordered pits in such positions is of so sporadic a nature as to give this feature no well-defined value, either for taxonomic or phylogenetic purposes! It may, nevertheless, be stated with respect to the pits on the tangential walls of the tra- cheids in general, that in their distribution they distinctly conform to the law governing simi'.'r structures on the radial walls. Reference to Cordaites acadianum shows that in the multiseriate pits of the hexagonal form these structures always preserve the spiral arrange- ment character- ist ic of the structures from which they fig. 12. sequou gi- were derived "antfa. Radial (plates 3-6), and this con- formity also ex- tends to the direction of the spirals which gen- erally ascend from left to right. The general law in this respect has already been formulated so fully Fi<;. 13. Sequoia gioantea. Tan- ''^ ^^ ^^^V (^^' '^3) as to make it gentiai section showing bordered unnecessary at this time to enter pits in the taneential walls of thp _ -a. . spring wood. «^ 4'^'"'"'* "f'he upon ,ts Consideration more in detail, beyond a reference to one or two special features and some apparently exceptional U hi e the spiral arrangement is always typical in such genera as Cordaites, Danimara, Araucaria, etc., it is not obvious in those cases where the pits are strictly ore-seriate and often remote section showing the bordered pits on the tangential walls , of the .spring wood. X 280 ©. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and a
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