Part 12. Plant Families And Higher Groups

12. Plant families and higher groups. On the same principle that similar species form a genus, similar genera are grouped into a family; and families which have certain fundamental points of similarity are associated to form still more inclusive divisions of the vegetable kingdom. Thus the oaks (Quercus), chestnuts (Castanea), beeches (Fagus), and other trees which agree in having their flowers in tassellike clusters, and their nut-like fruits held in something corresponding to a beech-bur, make up the beech family or Fagaceoe. The poplars (Populus) and willows (Salix) which also have tassel-like flower-clusters but only small seeds bearing slender silky hairs, constitute the willow family or Salicaceoe. Lilies and similar plants compose the lily family Liliaceoe; palms, the palm family, Palmaceoe; pine-like plants, the pine family, Pinaceoe, and so on. Plants like cabbage and mustard with flowers of cross-like form belong to the mustard family Cruciferoe.¹

¹ It will be noticed that the botanical name of the families is formed usually by adding the termination aceoe to the main part of the name of a typical genus of the family. This termination corresponds to the English suffix aceous, meaning "having the qualities or characteristics of." The name is thus of adjective form, the noun plantoe being understood. Hence the full name of the willow family would be Plantoe salicaceoe, meaning salicaceous (or willow-like) plants. In a few cases like Cruciferoe (from L. crux, crucis, a cross; fero, I bear) the name expresses a peculiarity of the whole family.

So closely similar to the Fagaceoe are the members of the birch family, Betulaceoe, that botanists find it convenient to group the two families together into the beech order or Fagales. Similarly the Pinaceoe and another family resembling these cone-bearing plants form together the conifers, pine order, or Coniferales.¹

¹ The termination ales in later botanical usage indicates the rank of order, but until recently has been used indiscriminately for various ranks.

All plants which agree with the Coniferales in having no cases to contain their ripening seeds are grouped to form the naked-seedworts or Class Gymnospermoe;² while all the orders which develop their seeds in closed cases comprise the case-seedworts or Class Angiosperme?.³ Both together include all flowering and seed-producing plants, and so constitute the flowering plants, seed-plants, seedworts, or Division Spermatophyta,⁴ which together with the various divisions of flowerless plants make up the vegetable kingdom or Kingdom Vegetabilia.

² Gym''no-sper'mae - Gr. gymnos, naked; sperma, seed.

³ An"gi-o-sper'mae - Gr. angion, a case.

⁴ Sper'ma-toph"y-ta - Gr. phyton, a plant.

From what has been said it is evident that even if we do not know the name of a plant much of importance may be told about it if we know the family to which it belongs, and quite a little if we know only its order or class. Regarding any plant the question, What is it? calls for much the same sort of answer as when we wish to identify a soldier. As with the latter we need to know the army, corps, brigade, regiment, battalion, and company to enable us to place him with military precision, so with the former to know its division, class, order, family, genus, species, and variety tells botanically its place in the vegetable kingdom. In knowing the position of a plant, however, there is this additional advantage that as resemblances and differences are expressed in the botanical groups to a much greater extent than in the military subdivisions we are just so much better informed regarding the true nature and peculiarities of the plant.