BOT.-VOL. II.] PEIRCE-SEQUOIA SEMPERVIRENS. lOI 



is true. In the first place, we do not know the actual func- 

 tions, and cannot determine the entire significance, of the 

 phloem tissues in higher plants. In the second place, so 

 long as Trelease (1894), or any one else, can say without 

 proof of error, that Leitneria floridana, a tree, contains no 

 sieve-plates and inferably no sieve-tubes, the elements of 

 phloem commonly regarded as most essential, it is impossi- 

 ble to conclude that sieve-tubes are indispensable or that a 

 phloem as well as xylem connection between host and para- 

 site is essential for complete parasitism. Until the chemical 

 physiology, and not the anatomy only, of the relation exist- 

 ing between parasite and host in Viscmn, Phoradendron, 

 Cuscuta is worked out, it cannot be known how significant 

 and important are the tissue connections effected by the 



haustoria. 



As to the significance of these tissue connections, the 

 conditions presented by the white redwood may furnish 

 some idea. The dependent white redwoods are branches 

 of independent parents and are therefore connected from 

 their beginnings, xylem with xylem, phloem with phloem, 

 and parenchyma with parenchyma, with their parents. By 

 means of these connections the adequate supply of foods, 

 as well as of food-materials and water, by the parent to its 

 offspring, from old redwood host to parasitic sucker, is 

 assured from the first. On the other hand, a parasite 

 attacking the tree from the outside must establish these 

 connections. It may estabhsh them only imperfectly, as in 

 Viscum, or completely, as in Cuscuta. The white redwood, 

 with its perfect connection with the parent, offers the coun- 

 terpart of the condition which accompanies complete para- 

 sitism, and though the leaves persist as such, they are struc- 

 turally no longer perfect leaves, and physiologically only 

 partly so. Because of its perfect connection with the host, 

 the white redwood is able immediately to develop some feat- 

 ures of the characteristic structure of parasites. 



This is especially interesting because the white redwoods 

 are the vegetatively produced offspring of independent 

 plants, themselves the descendants of generations of inde- 

 pendent plants. The suckers of redwoods inherit the 



