Vessels of the Onion. 1 7 1 
I have given a figure of the former case as none has hitherto 
been published (Fig. 2). 
The rows of cells end bluntly at the extreme base and 
apex of the leaf ; no sign of any connection whatever with 
either the vascular bundles or the assimilating tissue can be 
seen, nor do they follow the course of the bundles at all. We 
find them very early in the life of the plant. In the first leaf 
of the seedling, which pushes up through the soil as a pointed 
arch and subsequently carries, the seed up in the air, a longi- 
tudinal section shows the laticiferous cells in their usual 
position throughout the whole length of the leaf ; the trans- 
verse septa are here thin and unpitted. 
Contents. As Hanstein pointed out, the cells are filled with 
a more or less granular turbid fluid which appears on the 
cut surface of an onion as a pale milk ; in the green leaves 
the contents are clearer and more watery than in the succu- 
lent leaf-scales. I cannot find that any food-substances are 
present ; there is no starch or sugar, though glucose is present 
in large quantities in the surrounding cells. Fats cannot be 
detected; and the ordinary microchemical proteid-tests, e.g. 
Millon’s, and the xantho-proteic, give purely negative results, 
and the usual proteid-solvents, such as salt-solution (10 per 
cent, and saturated), 1 per cent, or 5 per cent, potash, cause 
no apparent diminution of the contents, if sections be watched 
under the microscope while running in the reagent. The 
action of 5 per' cent, potash for nearly two hours is without 
apparent effect. Carbohydrate, fatty and proteid-food-stuffs 
are therefore presumably absent, at any rate in quantities 
appreciable by the existing methods of microchemistry. The 
contents appear to consist merely of a resinous excretion 
soluble in alcohol. Hanstein says that calcium-oxalate never 
occurs, but it can be found in the laticiferous cells as well as 
in the surrounding parenchyma at the base of the succulent 
leaf, in the form of long crystals. 
Structural Changes . On first examining these cells 1 , there 
1 Vines and Rendle, Proc. of Camb. Phil. Soc., 1886. 
