Partial suppression of the leaf occurs sometimes in compound leaves, some or other of the leaflets of which are occasionally suppressed. Sometimes, as Moquin remarks, it is the terminal leaflet which is wanting, when the appearance is that of Cliffortia, at other times the lateral leaflets are deficient, as in Citrus or Phyllarthron. Ononis monophylla and Fragaria monophylla may be cited as instances of the suppression of the lateral leaflets. If the blade of the leaf disappears entirely, we have then an analogous condition to that of the phyllodineous acacias.
With reference to the strawberry just mentioned, Duchesne, 'Hist. Nat. Frais.,' p. 133, says that this was a seedling raised from the fraisier des bois, and the characters of which were reproduced by seed, and have now become fixed. The monophyllous condition has been considered to be the result of fusion of two or more leaflets, but however true this may be in some cases, it is not the case with this strawberry. M. Paillot states that he has found the variety in a wild state.[465]
In like manner varieties of the following plants occur with simple leaves, Rosa berberifolia (Lowea), Rubus Idæus, Robinia pseudacacia, Fraxinus excelsior, Sambucus nigra, Juglans nigra, &c.
In one instance seen by the writer every portion of the leaf of a rose was deficient, except the stipules and a small portion of the petiole. (See abortion.)
Meiophylly.—A diminished number of leaves in a whorl occasionally takes place; thus, in some of the Stellatæ, and frequently in Paris quadrifolia, the number of leaves in the verticil is reduced. Care must be exercised in such instances that an apparent diminution arising from a fusion of two or more leaves be not confounded with suppression.
Meiophylly of the calyx or perianth.—A lessened number of sepals is not a very common occurrence among dicotyledonous plants. Seringe figures a proliferous flower of Arabis alpina with two sepals only, and a similar occurrence has been noticed in Diplotaxis tenuifolia.
In Cattleya violacea the writer has met with a flower in which the uppermost sepal was entirely wanting, while two of the lateral petals were fused together. Moquin records that in some of the flowers of Chenopodiaceæ, in which the inflorescence is dense, a suppression of two or three sepals sometimes occurs. The species mentioned are Ambrina ambrosioides, Chenopodium glaucum, and Blitum polymorphum.
Meiophylly of the corolla.—Suppression of one or more petals is of more frequent occurrence than the corresponding deficiency in the case of the sepals. Among Caryophyllaceæ imperfection as regards the numerical symmetry of the flower is not uncommon, as in species of Cerastium, Sagina, Dianthus, &c. In Ranunculaceæ the petals are likewise not unfrequently partially or wholly suppressed. A familiar illustration of this is afforded by Ranunculus auricomus, in which it is the exception to find the corolla perfect.[466] Some varieties of Corchorus acutangulus in west tropical Africa are likewise subject to the same peculiarity. Amongst Papilionaceæ absence of the carina or of the alæ is not uncommon, as in Trifolium repens, Faba vulgaris, &c.
Moquin relates a case of the kind in the haricot bean, in which the carina was entirely absent, and another in the pea, where both carina and alæ were missing, thus reducing the flower to the condition that is normal in Amorpha and Afzelia. Suppression of the upper lip in such flowers as Calceolaria has been termed by Morren "apilary."