82 



HUTCHINSON'S POPULAR BOTANY 



FlO. 113. COLLENCHYMA OF THE 



COMMON SOW-THISTLE (Sonchus 

 asper). 



thing poured or put in).* Its cells are 

 long and tapering, and dovetail into one 

 another, and these are the leading charac- 

 teristics of prosenchyma. Yet there is no 

 absolute dividing line between the two 

 kinds of tissue, parenchyma passing into 

 prosenchyma, and prosenchyma into paren- 

 chyma, by endless gradations. 



The third tissue (fig. 113) has been named 



COLLENCHYMA, 



a word derived from two Greek words 

 kolla, glue, and enchuma, a word explained 

 above. The gluey something poured or 

 filled in is usually most abundant in the 

 corners of the cells, and is added by the 

 protoplasts with the view of strengthening 

 the delicate walls. The substance forms, 

 one might almost say, the corner-stones of 

 their little dwelling-houses. Collenchyma 



may be seen to advantage in the leaf-stalks of many Begonias, a trans- 



verse section being the best for examination. 



The name of the fourth kind of tissue is as tongue-tiring as the others, 



but we have met with it before 



SCLEREXCHYMA. 



It will be remembered that the cells from the gritty centre of a pear 

 (p. 31) were sclerenchymatous cells ; and it was pointed out that the name 

 is given to thick-walled woody cells in which the protoplasm has been all 

 used up. The section of a plum-stone (fig. 114) shows the same thing. 

 Sclerenchyma comprises, indeed, those tissues the cells of which have become 

 much hardened by secondary deposit, and which contain no protoplasm. 



It performs the mechanical office of support 

 an d strength, and is emphatically dead tissue, 

 the very opposite of the tissue to which we 

 next invite attention, namely 



MERISTEM. 



Meristem (Greek meristos, divided) is the 

 name given to growing tissue the cells of 

 which are continually dividing so as to pro- 



* The word was formed on the model of " paren- 

 chyma " with little regard for derivation (Text-book. 

 of Biology, p. 409). 



FIG. 114. SCLERENCHYMA FROM THE 



STONE OF A PLUM, MADE m> OF 



LIGNIFIED CELLS. 



