Vegetable Physiology. 



87 



to grow, stomata are found on the upper side, and roots on 

 the lower. If the plant be then turned over, so as to bring the 

 stomata on the under surface, and the roots in the air, it will 

 twist itself completely back again, so as to bring the surfaces 

 into their former position. 



Some observers have had the curiosity and the patience to 

 count the number of stomata contained within an inch square 

 of the surface of the leaves of various plants. The following 

 tabular statement has been collected from such observations. 

 The letters u. s. indicate the upper, and l. s. the lower side of 

 the leaf. 



JUMES OF PLANTS WHOSE PORES HAVE BEEN COUNTED. 



Andromeda speciosa, 

 Arum dracomtum, 

 Alisma plantago, - # 

 Amaryllis Josephiana, 

 Cobaea scandens, - 

 Dianthus caryophyllus, 

 Hydrangea quercifolia, 

 Ilex, the Holly, - 

 Peonia, the Peony, - 

 Pyrus, the Pear, 

 Syringa, the Lilac, - 

 Rheum, Rhubarb, - 

 Rumex, the Dock, 



u. s. 



None. 



8.000 

 12.000 

 31.500 

 None. 

 38.500 

 None. 

 None. 

 None. 

 None. 

 None. 



1.000 

 11.088 



L. S. 



32.000 



16.320 

 31.500 

 20.000 

 38.500 



160.000 

 63.600 

 13.600 

 24.000 



160.000 

 40.000 

 20.000 



The cuticle possesses several different kinds of appendages, 

 which this is the proper place to mention. These are hairs, 

 bristles, stings, prickles, scales, glands, &c. Hairs are constructed 

 in various ways. Sometimes they are composed of a single 

 cell, as in Fig. 8, a ; often of a row of cells, b, in which 

 case they appear like a tube divided by transverse partitions. 

 They may be branched, as c, or covered with small processes, 

 which are themselves branched, d, or they may be divided, as 

 in e. Hairs are generally acute, but often their point is blunt 

 or enlarged at the extremity, as/, secreting a viscid fluid, when 

 they are called glandular hairs. Sometimes they are tubular 

 and pointed, and fixed upon a gland containing an acrid fluid, 

 which, when the hair is touched, rises up, by the compression 

 of the gland, into the wound made by the point. In this case 

 it is called a sting, g, and must be familiar to every one who 



