1 66 HOW TO WORK 



fectly passive and arc btil carried in the moving stream. Sometimes 

 these are formed from the germinal matter itself, sometimes they are 

 foreign particles entering from without. 'Hie latter may be seen 

 commonly enough in the amacba. Pus and mucus corpu.scles-, and 

 many other forms of germinal matter, contain extremely minute 

 particles, the nature of which has not been positively determined, ;i> 

 well as foreign particles which become included by the mass pro- 

 jecting itself around them. 



The hairs from the flower of the Virginian spider-wort (Tradescantia 

 Virginica) a well-known garden plant, are beautiful objects for 

 studying the movements of the living germinal matter in the cell. 

 The transparent matter in active movement contains many minute 

 highly refractive particles, which enable one to detect the slightest 

 variation of the direction in which the stream sets. The young hairs 

 of the nettle, the cuticular cells of this and many other plants, exhibit 

 rotation. The movement can often be seen in the young, although 

 it may not be visible in the fully formed cells. 



In pi. XXXIX, fig. 245, a branch of anacharis alsinastrum is repre- 

 sented. It consists of long slender stems which bear a series of three 

 narrow leaves of a pale green colour at intervals of about a quarter 

 of an inch apart. The leaves when full grown seldom exceed a 

 length of three-eighths of an 'inch. Fig. 548 shows the irregular shape 

 and position of the cells in one of the leaves of this plant The 

 thickness of the central part of the leaf is composed of two layers of 

 such cells, but at the margin only -one layer exists. Fig. -24^ repre- 

 sents one of the hollow spines or hairs at the margin of the leaf of 

 the anacharis. It appears that when the circulating corpuscles 

 arrive near the apex of the spine where the cell wall is indurated, as 

 shown by a brown discoloration, they do not pass quite to the apex, 

 but are invariably hurried across the cell, as seen at b in the -Sgure. 

 The three drawings above referred to, have been taken from Mr. Wen- 

 ham's paper " On the Circulation in the Leaf Cells of Anacharis 

 Alsinastrum." (Mic. Journal, vol. Ill, p. 281.) 



In pi. XXXIX, fig. 246, is represented a hair or spine from the 

 stalk of Anchusa paniculata, one of the Boragineas, This is also 

 taken from a drawing by Mr. Wenham (Mic. Journal, vol. Ill, p, 49). 

 The mode of growth and circulation of the sap-corpuscles are well 

 shown. These accumulate and gradually become converted into the 

 tissue of which the spine is composed. Mr. Wenham well describes 

 this process as follows : a dense current of corpuscles travels along- 

 one wall of the spine constantly returning by the opposite side b, b. 

 At r, where the deposition occurs, there is a considerable accumula- 

 tion, and at the boundary where they are converted into the substance 



