378 



MANIPULATION. 



hundred to four hundred diameters, but in d it can only now 

 and then be shown. Each cell has its large nucleus and its 

 accompanying small globules, as in the other plants, some- 

 times even many currents are seen in the same cell. 

 " Throughout the plant," says Mr. Slack, " the circulation 

 may be shown, in the petal even when entire, and in all 

 sections made of the stem and leaves." 



Pentstemon. — Mr. Slack has also described the circulation in 

 a species of Pentstemon in the hairs taken from the throat of 

 the corolla. One of these is shown by fig. 251 ; when highly 



magnified, it is one continuous cell projecting from the cuticle. 

 In this hair the currents move in various directions, as shown 

 by the arrows— some pass to the top, whilst others do not 

 extend half way before they return, and very often two 

 currents unite to form one. Mr. Slack states that he never 

 observed a nucleus in any of these hairs. 



Groundsel— The. circulation in the delicate hairs found 

 upon the leaf stallss of the common groundsel, Senecio vulgaris. 



