Notice of Book. 135 
The remainder of Dr. Krabbe’s work, though touching on many 
points of great interest, will not require detailed consideration. 
Some of the points here discussed, as, for example, the causes of 
annual rings and the relation- of turgidity to growth, have only an 
indirect connection with the immediate subject of the paper. 
In my opinion it must be granted that Dr. Krabbe has succeeded, 
not only in demonstrating the occurrence of sliding growth, but in 
showing that it is probably universal among vascular plants, and that 
thus the difference between their tissues and the false tissues of the Fungi 
and Algae is only a difference of degree. Special cases, like that of 
Dracaena and its allies, will clearly require much further investigation, 
and in all cases of longitudinal sliding growth there is room for 
additional evidence from direct observations of the elements at various 
stages of development. 
In the light of the author’s researches it is clear, that greater im- 
portance must be attached to the independent growth of the individual 
cell than has been usual in recent years. The structure of the most 
important tissues depends to a great extent on the special mode of 
growth of certain of the constituent cells. 
The fact that sliding growth takes place between very young cells 
is also of interest as proving that the wall between them must be a 
double one, even at this early stage. This conclusion agrees with the 
observations of Wiesner 1 . 
The localised growth of certain portions of the cell-wall is no new 
discovery, but Dr. Krabbe’s observations supply additional instances 
of its occurrence. It is probable that the careful study of cases of 
this kind will confirm the authors conclusion, that the turgidity of 
the cell is by itself quite insufficient to account for the phenomena 
of growth. 
Dr. Krabbe is of opinion that continuity of the protoplasm through 
the cell-wall cannot exist in the case of any cells between which 
sliding growth takes place. In this I am unable to follow him. It 
is well known that the perforation of the sieve-plates is a secondary 
process, the plate at its first origin being a continuous cellulose wall. 
It appears quite possible that the same may be true of the more 
delicate perforations through which the protoplasm is continuous 
1 Untersuchungen liber die Organisation der vegetabilischen Zellhaut. Sitzungs- 
berichte der Kais. Akad. der Wissenschaft. Wien, 1886. 
