CELL COMMUNITIES: A CHAPTER ON TISSUES 



77 



\ve trust the reader will follow the description closely, as the points to 

 be touched upon are of great importance. "We will consider vessels first. 



To this end it may be well to take a backward glance for a moment. On 

 pp. 32 and 34 are illustrations of the spiral, annular, reticulated, and 

 pitted cells (figs. 54 and 57). Now, from all of these, vessels may be 

 formed. Place a lot of spiral cells on top of one another, and break away 

 the whole or greater part of 

 each of the partition walls, 

 and you will have a spiral 

 vessel (fig. 105, /). Do the 

 same with a number of 

 annular cells, or reticulated 

 cells, or pitted cells, and you 

 will have annular vessels, or 

 reticulated vessels, or pitted 

 vessels, as the case may be 

 (fig. 105, c and g). Of course 

 this could not be done in 

 reality, the vessels being far 

 too small ; but we use popu- 

 lar language. Hooke esti- 

 mated that a cubic inch of 

 oak contains upwards of 

 seven millions of vessels ; 

 and another of the old micro- 

 scopists, Leuwenhoek, com- 

 puted that the bole of an 

 Oak, only four inches in 

 diameter, contains about 

 two hundred millions ! We 

 are not sure whether 

 Damory's Oak in Dorsetshire 

 is still standing; but this 

 tree not many years ago 

 measured eighty-four feet 

 in circumference, and it 

 was then shown by a labori- 

 ous calculation that more 



than 240 millions of miles of vessels were packed in a single foot's length 

 of the stem, and that if the vessels contained in the whole tree could be 

 placed end to end in a single line, they would have made a communica- 

 tion backwards and forwards between the sun and every planet in. the 

 system! The few thousand miles of piping which underlie London look 

 rather paltry in comparison with this. 



Photo &y] \_E. Step. 



FIG. 107. CAPER SPURGE (Euphorbia lathyris). 



A plant frequently grown in gardens, but locally wild in the south of 



England . Its seed-vessels have been used as a substitute for capers, 



but they are of a poisonous nature. About one-twelfth of the natural 



size. S. EUROPE. 



