70 



BOTA A r. 



This tissue makes up the whole of the substance of many 

 of the lower plants. In the higher plants the essential por- 

 tions of the assimilative (green), vegetative (growing), and 

 reproductive parts are composed of parenchyma. 



Instructive examples of parenchyma may be obtained in the growing 

 ends of shoots (Fig. 53) and in the pith of Dicotyledons, in the ends of 

 young roots t. g., of Indian corn in the green pulp of leaves, iu the 

 pulp of fleshy fruits, and in the substance of young embryos. 



10O. Collenchyma. The 

 cells of this tissue are elon- 

 gated, usually prismatic, and 

 their transverse walls are most 

 frequently horizontal, rarely 

 inclined. With few excep- 

 tions* there are no intercellu- 

 lar spaces. The walls are 

 greatly thickened along their 

 longitudinal angles, while the 

 remaining pans are thin (Fig. 

 21. p. 30). The cells con- 

 tain chlorophyll, and retain 

 the power of fission, f Wet 

 specimens show by transmit- 

 ted light a characteristic blu- 

 ish white lustre (Figs. 54 and 

 55). 



Colleuchyina is found be- 

 neath the epidermis of Dico- 

 tyledons (and some ferns). 

 usually as a mass of conside- 

 rable thickness, and is doubtless developed from parenchyma 

 for the purpose of giving support and strength to the epi- 

 dermis. 



F5g. 54. Trans yerse section of collen- 

 chj-ma (00) of the stem of R'hinocyttu 

 lobata. wet with water, and the arigks 

 jrrcatly swollen. ei>. epidermis, with 

 thickened outer wall x TOO. " 

 drawing by J. C. Arthur. 



From a 



* In the eollenrliyma of SilpMum pfrfoliatum there are many lon- 

 gitudinal intercellular spaces of various sizes ; in fptnmrn purptirea 

 there are minnte ones. 



f De Bary states that collenchyma-oells are capable of fission. 

 ' Verjjleichende Anatomit- dr r VegetatiousorgaDe der Phauerogam. n 

 und Faroe," p. 126. 



