36 A HALF-HOUR WITH THE 



the case of the oak, figured at figure 55, plate 3. 

 These are called " ducts." Such clncts may be well 

 observed in the transverse section of the common 

 radish, as seen at figure 51, plate 2, and in other 

 roots. These ducts are often marked by pores, or 

 dots, and are hence called " dotted ducts." These 

 dots are the result of deposits in the interior of 

 the tube of which the duct is formed, and a great 

 variety of such markings are found in the interior 

 of vascular tissue. One of the most common 

 forms of marked vascular tissue is that which is 

 called glandular woody tissue, of which a figure is 

 given at 54, plate 3. This kind of tissue is found 

 in all plants belonging to the cone-bearing, or fir 

 tribe of plants. In order to discover it, recourse 

 need not be had to the garden for growing plants, 

 as every piece of furniture made of deal wood will 

 afford a ready means of obtaining a specimen. All 

 that is necessary to observe the little round disks 

 with a black dot in the middle is to make a thin 

 longitudinal section of a piece of deal, and place it 

 under a half or quarter-inch object-glass, when 

 they will be readily apparent. The application of 

 a drop of water on the slide, or immersing them 

 in Canada balsam, will bring out their structure 

 better. 



If we take the leaf-stalk of a strawberry, or of 

 garden rhubarb, and make a transverse section all 

 round, nearly to the centre of the stalk, the lower 

 part will at last break off, but be still held to the 

 upper by very delicate threads. If we examine 

 these threads, we shall find that they are fibres 

 which have been left by the breaking of the vessel 

 in which they were contained : such fibres are seen 

 at figure 48, plate 2. These vessels are called 

 " spiral vessels," and are found in the stems and 

 leaves of many plants. They are seen rolled up as 



