68 PRACTICAL BOTANY 



in the centre of the bud will be found the elongated conical and 

 colourless apical cone. Cover with a cover-slip, and examine 

 it under a low power : the smooth cylindrical apical cone will 

 be well seen, the inner tissues of it being marked by a reticu- 

 lum of dark lines : these are the intercellular spaces filled with 

 air. 



Note especially the leaves, which appear as rounded out- 

 growths laterally on the axis : the larger ones are seated lower 

 down the axis, and they are successively smaller as the aoex is 

 approached. 



III. Cut median longitudinal sections of the apical bud of 

 Hippuris, so as to pass through the elongated apical cone -, 

 treat with potash, or with " eau de javelle," and mount in 

 dilute glycerine. Examine first with a low power, and ob- 

 serve 



1. The axis, which is wide below, but tapers upwards to the 

 rather elongated apical cone (ptmctum vegetationis). The 

 axis is composed of the several tissues already noticed. Note 

 especially in the lower part of the section 



a. The rectangular intercellular spaces, divided transversely 

 by diaphragms at the nodes. 



b. The axile vascular cylinder, which may be followed far up 

 into the apical cone, and which gives out lateral branches to 

 the leaves. 



2. The leaves, diminishing in size towards the apex. Note 

 the scale-hairs about the bases of the leaves. 



Put on a high power, and examine the apical cone. Note 



1. The dermatogen, a continuous layer of cells, which covers 

 the apical cone externally. Trace it backwards from the apex : 

 it will be seen to give rise to the epidermis.* 



2. The periblem, consisting of 4-5 layers of cells, which may 

 be traced backwards, and be thus shown to give rise to the 

 cortex. 



3. A central cylinder of plerome, which is continous with, 

 and gives rise to, the vascular cylinder (compare the diagram 

 Fig. 3, p. 48). 



Note that the leaves originate from the outgrowth of the 



