223 
Notice of Book . 
from the tube, and in providing material for the formation of callus in 
order to dose the plates when necessary. From the fact that the 
upper phloem of the bicollateral bundles in the leaf of Cucurbiia is 
already empty at a time when the normal lower phloem is in full activity, 
it is inferred that the former fulfils its function during the development 
of the leaf, serving to conduct to it the necessary food-supplies, while 
the normal phloem is alone concerned in conveying the products of the 
leafs own assimilation. It will be interesting to observe how far this 
distinction holds good in other cases of double phloem. 
In describing the anatomy of various Ranunculaceae the author 
calls attention to the close agreement in structure between the vascular 
bundles of this order, and those of the Monocotyledons. 
The first monocotyledonous type described is the familiar Zea Mats. 
The course of the vascular bundles is traced in detail, and it is shown 
that each bundle thins out greatly before fusing with one below it. 
Hence at every point of fusion there is a marked constriction of the 
water-conducting channels. From this fact, as well as from many 
other observations and experiments pointing in the same direction, 
the author infers that very narrow tracheal strands are sufficient to 
conduct the ascending current of water. The large vessels are im- 
portant for storage rather than for conduction. 
The phloem of the bundle, as well as its xylem, tapers in the down- 
ward direction. The effect of this is that each row of sieve-tubes and 
companion-cells is in its turn brought into contact with the surround- 
ing parenchyma, to which it can thus pass on the nitrogenous food- 
supplies. 
The anatomy of several Palms is investigated, and it is shown, in 
agreement with Eichler, that when growth in thickness takes place it 
is due entirely to the extension of the inter-fascicular parenchyma. 
The Monocotyledons with true secondary thickening receive much 
attention. The author points out that the thickening-ring here differs 
from the true cambium of Dicotyledons or Gymnosperms in the fact 
that there is no single initial row of cells to the divisions of which 
all the secondary tissues can be traced. On the disputed question of 
the nature of the secondary c tracheides ’ in these plants, Prof. Stras- 
burger entirely confirms the opinion of Krabbe and Roseler, that these 
elements are really tracheides, formed by the elongation of single cells, 
and not 1 short vessels/ arising by cell-fusion, as was maintained by 
Kny and others. Some valuable observations on the remarkable 
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