modified in somefiber, oilseed and marijuana selections, as noted later. In common
with many other species with both domesticated and wild populations, the leaves of
the domesticate tend to be larger and the leaflets broader, apparently to provide a
greater photosynthetic area (Small 2015 ).
The“seeds”(achenes) of weedy plants differ dramatically from those of plants
domesticated forfiber, oilseed or illicit drugs (Small 1975 ; Fig.1.3). Usually the
seeds of wild plants are smaller than 3.8 mm in length, in contrast to the larger
seeds of domesticated selections. Large size of seeds in domesticated plants is
usually the result of selection for a desired product in the seeds (frequently for
food), but also larger seeds provide a greater store of food reserves for successful
germination and establishment. Kluyver et al. ( 2013 ) proposed that ancient agri-
cultural practices buried seeds quite deeply, leading to an increase in seed size
under domestication so that seedlings would have the energy to grow out of the soil.
Most wild plants cast off their seeds or fruits at maturity, in order to disseminate
them. Selecting mutations that inactivate the separation mechanisms (abscission,
i.e. breaking away of fruits at their base so they fall away; or dehiscence, i.e.
opening of fruits to release seeds) greatly facilitates harvest by humans because the
Fig. 1.2 Growth patterns of weedy forms ofCannabis sativa.aStrong branching pattern typical
of a well-developed, open-grown, weedy female plant (cultivated near Toronto, Canada from seeds
from Georgia, Eurasia).bA dwarfed, unbranched female plant (the type specimen ofC. ruderalis
Janischevsky; a male branch from another plant is atright). Note the narrow leaflets, typical of
weedy plants
1 Classification ofCannabis sativaL. in Relation... 9