THE MAGAZINE 



OF 



FEBRUARY, 1837. 



ORIGINAL COMMUNICATIONS. 



Art. I. Microscopic Observations. No. I. By A Corres- 

 pondent. 



Whoever has taken any notice of the forms and modifica- 

 tion of leaves, must have observed a diversity of pubescence in 

 the greater or less number of hairs Avhich constitute that peculiar 

 and organic structure. Thus the beautiful cilise on the margin of 

 some, as O'xahs, sp., the woolly appearance on others, Ferbascum, 

 Gnaphalium, -S'tachys, the sericious clothing of Leucadendron 

 argenteum, the soft and close pile of Pycnanthemum, the fragrant 

 apparatus of Jl/entha, and the poisonous, stinging armature of 

 C/rtica and Lodsa, are familiar examples. The functions such 

 organs perform in the general economy of the plants have not 

 been satisfactorily ascertained. Absorption and exhalation have 

 been supposed to be effected by their agency. As a protection 

 from undue heat or moisture they have been considered of im- 

 portance. For the former purpose they must serve as a defence 

 from the sun to those minute pores which exist on the surface of 

 the leaf. In the latter instance they should answer a similar pur- 

 pose to the glaucous investment on smooth foliage, technically 

 called the bloom, which, though easily removed, has an astonish- 

 ing power in the repulsion of water. 



Notwithstanding most plants are furnished with pubescence in 

 •some stages of growth, or on some parts of their structure, yet 

 whole familes and groups are entirely destitute of it. Such are 

 the thick leaved and succulent kinds. Even here we have nota- 

 ble exceptions in the fierce and strong-armed species of the 

 Cacti, many of which are completely invested, on their leafless 

 stems, with a larger and smaller scries of prickles, improperly, 



VOL. III. NO. H- 6 



