. Botanical gazette. Plants. 220 BOTANICAL GAZETTE [SEPTEMBER are they laid down at regular intervals of time. The plant which was studied was more than a century old and yet had but 3 vas- cular cylinders. Doubtless the cortical cylinders are related to certain activities of the plant alternating with long periods of rest which may vary greatly in point of duration. Summary and conclusions 1. The paper deals with the adult stem of Cycas media, particular attention being paid to the xylem and phloem details of the normal and first cortical cylinders. 2. Not all the vascular cylinders are of eq
. Botanical gazette. Plants. 220 BOTANICAL GAZETTE [SEPTEMBER are they laid down at regular intervals of time. The plant which was studied was more than a century old and yet had but 3 vas- cular cylinders. Doubtless the cortical cylinders are related to certain activities of the plant alternating with long periods of rest which may vary greatly in point of duration. Summary and conclusions 1. The paper deals with the adult stem of Cycas media, particular attention being paid to the xylem and phloem details of the normal and first cortical cylinders. 2. Not all the vascular cylinders are of equal longi- tudinal extent. Only the normal one begins its differ- entiation as high up as the meristem, the others begin- ning their differentiation suc- cessively lower, and each one in the cortex outside the next inner cylinder. The normal cylinder, therefore, is the only one which would be expected to originate with a procam- bium, and the only one which could develop protoxylem and protophloem. 3, Following up these expectations, both protoxylem and pro- tophloem were found to have been developed during the early activities of the normal cylinder. Protoxylem elements are usually scalariform, although hints of spiral tracheids are more or less frequent. Primary xylem is scalariform and secondary xylem is characteristically Fig. II.—Cycas media: transverse section of stem, showing tip of phloem belonging to second cylinder; c, cortical cells; b, suberized bast fibers; Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Hanover, Ind. : J. M. Coulter
Size: 1256px × 1989px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcollectionbiodiversity, bookcollectionnyb, booksubjectplants
