ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 479 



of Gelsemium sempervirens. Microscopic examination shows that there 

 are ordinarily four or more points, at which a well-defined swelling 

 curves inward from the circumference of what should be the pith- 

 cavity. These swellings resolve themselves into (1) toward the 

 centre an imperfectly defined membrane, resembling cuticle, which 

 was not always present ; (2) one or more rows of large cells like the 

 parenchyma under the epidermal layer ; (3) several poorly defined 

 layers of smaller cells, such as often mark the limits of growth in 

 bark ; (4) the frequent presence of bast-fibres or of sclerenchyma- 

 cells ; and (5) an evident layer of thin-walled, square cells, closely 

 resembling those of the external cambium, and showing signs of 

 division. These facts explain why the pith is constantly encroached 

 upon until it at length almost disappears. The medullary rays dip 

 down through and widen out in this inner cambium inivardly, just as 

 they do outwardly in the usual form. 



The author also records the presence of considerable quantities of 

 chlorophyll in the pith ofLycium vulgare. This is not confined to the 

 smallest stems, but is found also in those of over 1/4 in. in diameter, 

 and where of course a considerable belt of hard wood is found between 

 the pith and the outer zone, where chlorophyll is expected. It was 

 also observed that the chlorophyll was not in the form of bodies but 

 diffused in character, as it is said to be in some infusorians. The 

 cells of the pith show in winter abundance of protoplasm which has 

 the nucleus on one side, and very striking bands extending thence 

 across the cell to the further cell. 



Penetration of the Mechanical Ring- for the Transport of Food- 

 material.* — Dr. A. Tschirch describes the mode in which the pro- 

 ducts of assimilation pass from one part of the plant to another 

 through the barrier presented by the " mechanical ring " of hardened 

 impermeable strengthening tissue. This is effected (a good example 

 is afforded by the flat phylloclades of MiililenhecMa platyclados) by 

 the replacement here and there of these strengthening cells by " trans- 

 mission-cells " (Durchlasszellen) which are thin-walled on all sides 

 or at least on one side, and are usually situated near to the vas- 

 cular bundles. These are generally accompanied by other cells in 

 their immediate neighbourhood, the " collecting-cells '' (Sammelzellen), 

 roundish cells, containing no chlorophyll, though lying in the midst 

 of green tissue, but densely filled with protoplasm. These cells 

 usually lie in longer or shorter rows leading from above and below 

 to the spots where the mechanical ring is broken throui^h ; and the 

 cells of the green tissue often converge towards them like a star ; 

 their purpose is to collect the products of assimilation and conduct 

 them to a perforation through the mechanical ring. 



Stolons of Sagittaria sagittsefolia.f— Dr. C. Miiller describes at 

 length the morphology and the anatomical structure of these organs, 

 in relation to the epidermis, the hypodermal layer, the fundamental 

 tissue, the laticiferous canals, and the vascular bundles. 



* Ber. Deutsoh. Bot. Gesell., ii. (1884) pp. xxvii.-xxxi. (1 pi.), 

 t SB. Gesell. Natuif. Freunde Berlin, 1884, pp. 165-79. 



