BOTANICAL SUBJECTS, 277 



XIV.— TRICHOMES, PRICKLES, GLANDULAR HAIRS, 



SPORANGIA, &c. 



Trichomes. 



Asa Gray, iu his work on " Structural Botany," p. 209, says, 

 " Bristles and hairs in all their variety and modifications are 

 properly outgrowths of the epidermis only, and therefore consist 

 of extended cells, single or combined, unaccompanied by vascular 

 or woody tissue. To them has been given the general name of 

 trichomes, that is, structures of which hairs are the type." 



In examining some Jonquils, I found that within the spathe, 

 besides flowers, there were long hairs, representing spathels, or 

 aborted spathes. These hairs were so fine that they were attracted 

 by the ebonite mounting (evidently electrified) of my lens. 

 Structurally they were hairs, and, therefore, might serve as types 

 of trichomes, yet, morphologically, they were spathes or bracts ! 



At p. 210, Asa Gray says, " But in some bristles, such as those 

 of Drosera, a subjacent stratum of tissue enters, including one or 

 more ducts, or even some woody tissue. Prickles are of this class.* 



Such outgrowths may even be formed in regular 



order, as the prickles on the calyx-tube of Agrimonia, and scales 

 on the acorn-cup of oaks, and yet have no morphological 

 importance." (!)t 



" Structural difference between trichomes and out- 

 growths {Emergenzen of the Germans) is not absolute, and the 

 morphological distinction must rest upon other ground than 

 anatomical structure." 



* " It may readily be demoustrated that the prickles of the Kose and 

 Rubus arise not from epidermis only, but also from the i?ubjacent tissue of 

 the cortex" (Bower, " Pract. Bot.," p. 147). 



f In my opinion the " regular order " has a great morphological 

 significance. 



