290 A TEXT-BOOK OF BOTANY. 



LIGNIFIED HAIRS. In some seeds, as in nux vomica, the hairs 

 are strongly lignified, as are also the bases of the hairs of Stro- 

 phantus hispidus. This is due to a lignocellulose modification of 

 the wall, and, since broken hairs look more or less like fibers, one 

 might easily be led astray in the study of powdered drugs. It is 

 not usual to make a microchemical study of the walls of non- 

 glandular hairs, but this subject is well worthy the attention of 

 investigators. 



FALSE PLANT HAIRS. While it is impossible for the careful 

 student of plant morphology to mistake anything else for plant 

 hairs, it is, nevertheless, worth while to call attention to some of 

 the mistakes that are liable to be made. In works on systematic 

 botany sometimes occur contradictory statements concerning the 

 abundance or scarcity of hairs, especially as they relate to the 

 flower. In a superficial examination, for instance, in the violets, 

 large masses of germinating pollen grains with their tubes matted 

 together are not at all uncommon in the throat of the corolla, and 

 these have been mistaken for hairs. Furthermore, the mycelia 

 of fungi may be mistaken for hairs, especially in young seedlings, 

 as of hyoscyamus, belladonna, etc., where thread-like delicate 

 branching hairs may occur. In the examination of economic prod- 

 ucts, especially powdered drugs and spices, mistakes of this kind 

 may occur, unless the student has devoted some attention to this 

 study. In all studies of plant h^irs the student should carefully 

 locate the summits and bases, and unless these can be recognized, 

 or if broken made to correspond to each other, one cannot say 

 that hairs are present. 



CORK CELLS replace the epidermal cells of roots and stems that 

 persist year after year. They are formed, as has already been 

 stated, from a distinct meristem, called the phellogen. Cork cells 

 differ from the epidermal cells in that the walls are uniformly 

 thickened and on surface view are polygonal in shape. The walls 

 consist of suberin, a substance allied to cutin; in some instances 

 they also contan lignocellulose, forming cork stone-cells, as in 

 asclepias and calumba. The young cells may contain a thin layer 

 of cytoplasm and a nucleus; they usually also contain brownish 

 masses of tannin or tannin-like compounds, and occasionally crys- 

 tals of cerin or calcium oxalate. 



