Types and Purposes of Cannabis Trichomes
Trichomes are external extensions that appear on the leaves, stems, bracts, and blooms of many different plants including cannabis. Up close and personal under a microscope, these floral glands have a ghoulish appearance (see above photo for the spooky proof), and it may be no natural coincidence as trichomes’ purpose in nature is to frighten away potential predators, among other things. If not seen as microscopic ghosts, trichomes often appear like hairs, glands, or bulbs covering different parts of the plant. They develop into the resin producing and excreting components of cannabis that create and excrete desirable cannabinoids and terpenes.
Cannabis trichomes can be initially distinguished into two distinct categories — glandular and non-glandular trichomes. Among these two distinctions come six types of trichomes found within cannabis: unicellular non-glandular trichomes, cystolythic trichomes, capitate-sessile trichomes, capitate-stalked trichomes, simple bulbous trichomes and complex bulbous trichomes. 
Non-glandular trichomes serve to scare away potential predators such as insects and birds as well as defending the plant from environmental stressors. This variety of trichome functions as a type of shield on the outside layer of a plant, working to provide protection from intense ultraviolet (UV) rays emitted from the sun. Amongst these non-glandular trichomes, unicellular varieties are the first to develop on the plant and serve to guard against UV rays and regulate temperature, while cystolythic trichomes provide protection from predators. [2,3]
Glandular trichomes are responsible for the sticky secretions often associated with cannabis and produce and store the resin that contains most of the cannabinoids, terpenes and flavonoids desirable for consumption. The three varieties of glandular trichomes that secrete resin are capitate-sessile, capitate-stalked and bulbous trichomes. The trichome heads, or glands, are the specific secretory structures in which resin containing cannabinoids and terpenes can be found. Capitate-stalked trichomes and capitate-sessile trichomes both produce cannabinoids though capitate-stalked structures produce these compounds in higher amounts. Bulbous trichomes are very small and produce insignificant amounts of cannabinoids. 
- Andre, Christelle M., et al. “Cannabis sativa: The Plant of the Thousand and One Molecules,” Front Plant Sci, vol. 7, no.19, 2016. Times Cited = 156 Journal Impact Factor = 4.298
- Hall, David, et al. “Epifluoresecence and Stereomicroscopy of Trichomes Associated with Resistant and Susceptible Host Plant Genotypes of the Asian Citrus Psyllid (Hemiptera: Liviidae), Vector of Citrus Greening Disease Bacterium.” Journal of Microscopy and Ultrastructure, 6, no. 1, 2017, pp. 56-63. Times Cited =3 Journal Impact Factor = N/A
- Potter, David J. “Cannabis Horticulture.” Handbook of Cannabis, edited by Roger Pertwee, Oxford University Press, 2014, p. 68. Google Books.
Image Source: (Graphic 1)