Premise of research. Secondary phloem produced by a bifacial vascular cambium is the distinctive feature of lignophytes, the group that comprises the seed plants and the progymnosperms. Because ...

This is a preview. Log in through your library . Abstract Specimens with well-preserved phloem tissues of the pteridosperm Callistophyton boyssetii from coal balls in the Herrin no. 6 Coal of Illinois ...

Phloem diseases, including the economically devastating citrus greening, are particularly difficult to study because phloem cells -- essential for plant nutrient transport -- are difficult to access ...