ZUOLOG-Y AND BOTANY. MICROSCOPY, ETC. 205 



peculiarity in staining makes it possible to follow the diflFerent transfor- 

 mations of the vacuolar system, and it is found that mitochondrias, 

 chondriocontes, and chondriomites are transformed so rapidly into each 

 other, often ramifying and anastomosing into a iine network, that it is 

 impossible to regard them as being of the nature of plasts. On the 

 other hand, it is easy to trace the transformation of the elements of the 

 chondriome into ordinary vacuoles. The metachromatin solution is 

 conveyed to those parts of the cell where there is least resistance, and 

 during cell-division is transferred from one cell to another ; it is 

 opposite in action to the cytoplasmic fluid, and has a certain osmotic 

 power. The metachromatic corpuscles are formed in the vacuoles at the 

 exnense of the metachromatin. 



Structure and Development. 

 Vegetative. 



Development of Root-tip in Sagittaria.* — R. Soueges contributes 

 a further note upon the embryogeny of the Alismaceas. The writer has 

 studied the development of the root-tip of Sagittaria sagittsefolia, and 

 finds that the low'er cell of the pro-embryonic tetrad gives rise to the 

 greater part of the hypocotyl, the hypophysis, and the suspensor. The 

 hypophysis is of complex origin, for it arises from two cells of different 

 ages. The four initial-cells of the root-cap serve only for the increase 

 of the number of layers of this tissue ; they divide first by vertical and 

 subsequently by tangential walls. It would appear that those authors 

 are wrong who regard these cells as having the same functions as in 

 other Angiosperms. 



The present note will be followed shortly by a full account of the 

 work done in connexion with the embryogeny of Sagittaria. 



Distinctive Characters of Woods of North American Platanus.f 

 W. D. Brush has studied the wood of three species of North American 

 " sycamores" — viz. Platanus occidentaUs, P. Wrightii, and P. racemosa — 

 in order to discover some distinguishing characters which would serve 

 for identification. The chief of these characters are the sapwood, the 

 heartwood, and the size of the pith-rays. There is no well-defined limit 

 between the sapwood and the heartwood, but the former occupies only a 

 thin zone and is usually of a different colour. In the first species the 

 sapwood is light brown and the heartwood is of a reddish tinge ; in the 

 other species the sapwood is yellowish and tiie heartwood is darker, but 

 slightly tinged with red. In the eastern species the annual rings are 

 less well-defined than in the other species, but the pith-rays are larger 

 and darker. In tangential section the pith-rays are broadest horizon- 

 tally and lowest vertically in P. occidentaUs ; . in P. racemosa they are 

 narrowest horizontally and highest vertically. In P. occidentaUs the 



* Comptes Rendus, clxvi. (1918) pp. 49-52. 



t Bot. Gaz., Ixiv. (1917) pp. 480-96 (7 pis. and 3 figs.). 



