478 EECORD OF CURRENT RESEARCHES RELATING TO 



between the two ends of a growing organism, but also between an 

 anterior and posterior side, giving rise to a right and left half, wbenco 

 sucb a mode of growth may fairly be called symmetrical or bilateral. 

 The author proposes to restrict the term dorsiventral to those cases of 

 bilateral structure where the upper and under, or dorsal and ventral 

 surfaces exhibit organic differences, as where the shoots which proceed 

 from them are of a different nature, or where one surface only produces 

 shoots of any kind. 



Observations made chiefly on the Marchantiaceae, Zostera, Urtica, 

 Dorstenia, and Hyoscyamus, have led Professor Goebel to the following 

 general conclusions : — 



1. Just as there are radiar and bilaterally symmetrical (or zygo- 

 morphic) flowers, and organs of radiar and dorsiventral structure, so a 

 distinction may also be drawn between radiar and dorsiventral 

 branching. Dorsiventral branching is indicated by the different sides 

 of the primary organ (the ventral and dorsal side) behaving differently 

 in relation to the production of lateral branches, as in Caulerpa and the 

 Ehizocarpese, or by only one side producing lateral branches, as in the 

 inflorescence of the Borraginete. 



2. Organs with dorsiventral branching occur in all forms of plants, 

 from the simplest to the most complicated; the spiral theory pro- 

 pounded in the latter case is incorrect, in relation not only to the 

 history of development, but also to the supposed universality of the 

 radiar type. 



3. The mutual relations of leaf and shoot in dorsiventral organs 

 are usually dependent on the total symmetry of the shoot-system. 



4. Dorsiventral organs exhibit their dorsiventral structure in rela- 

 tion either to the substratum or to their primary organ. 



5. In all cases that have been examined it has been determined that 

 dorsiventral branching does not depend on subsequent displacement 

 or cohesion, but is a peculiarity of the growing point. When displace- 

 ment, &c., occur, and bring about a dorsiventral position of organs 

 which originated in a radiar manner, this can easily be made out. 



6. A distinction must be drawn between apical and intercalary 

 growing points, and between shoots which spring from intercalary 

 growing points and from intercalation. The former arise in progres- 

 sive order approaching the growing point. The acropetal develop- 

 ment of lateral organs is only a special case in which the growing 

 point has an apical position; and the same order of development 

 occurs also when the growing point has a basal position ; and the two 

 are therefore comprised in the general term progressive development 

 of organs. Intercalary growing points with progressive development 

 also originate from apical growing points ; they occur not only in 

 Algae, as Ectocarpaceae, but also in Angiosperms, as in the inflo- 

 rescence of Ficus carica, in the leaf-axils of Aristolochia, Menispermum, 

 &c., and in flowers. 



Leaves of Conifers.*— Dr. M. T. Masters has observed the fol- 

 lowing correlation between the various characters respectively of the 



* ' Joum. Linn. Soc' (Bot.), xvii. (1880) p. 547. 



