570 SU.MMARY OF CURKENT RESEARCHES RELATING TO 



BOTANY. 



GENERAL, 



Including the Anatomy and Physiology of Seed Plants. 



Structure and Development. 



Vegetative. 



" Sanio's Bars " in Pinus.* — AV. Rushton has reinvestigated the 

 development of " Sanio's Bars " in order to discover their origin. Twenty- 

 five species of Pinus were examined, but the present results are based 

 upon P. Inops, which exhibited the largest number of bars and gave 

 the clearest results. The bars are small rods passing through the 

 tracheides, cambium and phloem elements ; in the cambium they are 

 thin and solid, but in the phloem and sylem they are more or less 

 hollow. They become thicker by deposits of layers of the substance of 

 the cell-wall, i.e. cellulose in the cambiam and phloem, lignified material 

 in the xylem. They possibly have their origin in the small masses of 

 protoplasm which frequently surround them in the cambium cells. 



Anatomy of Piper.f — R. E. Hoffstadt has studied the vascular 

 anatomy of Piper methysticum in order to give " a modern interpretation 

 to the vascular structure, and to ascertain whether the stem keeps pace 

 -with the gametophyte of the group." The stem has two systems of 

 "bundles, i.e. a single-layered peripheral system and two rows forming a 

 medullary system. The peripheral bundles are either large and primary 

 or small and secondary, the latter being branches of the former. The 

 bundles are of foliar origin and of collateral, endarch structure : after 

 ■entering the stem they traverse the periphery through one internode, 

 and the pith through two inlx-rnodes. Both peripheral and medullary 

 bundles show anastomoses. The pericycle is represented by a few 

 lisnified cells outside the bundles ; there is no differentiated endodermis. 

 Increase in thickness of the stem is due to cambial activity m the pith ; 

 interfascicular cambium appears late in the internodes, and still later in 

 the nodes ; it cuts off segments only on one side. Leaf-traces are 

 numerous ; the base of the leaf is sheathing, and the vernation is 

 iuvoluie. The buds vary in number and position. 



Piper iimhellatmn is found to differ from P. methysiicum in having 

 (1) Only one ring of medullary bundles ; (2) mucilage-canals running 



* Ann. Bot., xxx. (1916) pp. 419-27 (4 figs.), 

 t Bot. Gaz., Ixii. (1916) pp. 115-32 (23 figs.). 



