HS 



■v 



TERATOLOGY 



mon on conifers (especially Abies) and some deciduous 

 trees. Similar deformations are sometimes due to in- 

 sect agency, or to unknown causes. For example, a 

 simple inflorescence may develop flower-clusters instead 

 of single flowers, e.g., in the 

 sf^Sj'&jb. common plantain. 



' '"-wjgrX '■ Proliferation is continued 



| .» .;ffi'\ growth of the axis or the de- 



\:.\,0jji' £j velopment of a branch from 



'^VrfSlSf 1 ^- growing points which usually 



^^^wSggfc^ , ■ i 1 1 1 c - 1- chi ii"! form or remain 



tt.\i :;1 ' 'i"i man: . I \ :i : : 1 1 ' !■ ■ . l!" 



,./ ,i^X' growing point of the axis of the 



'■*j$m flower is usually obliterated in 



"-.: : .' the t'ornialion of the pistil, but 



. _ : '.:J_v' -' lit the pear, apple ami straw 



Br berry it frequently continues 

 its growth through the flower 

 and may even become a leafy 

 shoot beyond the fruit. Pro- 

 liferation may also occur by 

 the contiuued growth of the 

 axis through a compact rlower- 

 cluster, like the head of Com- 

 ... extension of the axis positee; or by the development 

 of growth with an added of branches m the axils ot the 

 whorl of carpels. petals and sepals, e. g., in cauli- 



flower, or the rose shown in 

 Pig. 2482. Some double flowers are made "extra dou- 

 ble" by this sort of proliferation. Proliferation is said 

 to occur in almond embryos, one or more smaller 

 embryos arising from the normal one ; but the state- 

 ment lacks continuation and such an origin is highly im- 

 probable. When proliferous branches show a tendency 

 to separate easily and to develop roots, or when they 

 become bulb-like, so that they reproduce the plant read- 

 ily when separated, the plant is said to be viviparous. 



4. By various causes complete non-development of 

 organs (suppression) may occur; or an organ maybe 

 arrested at any stage of its growth or be dwarfed. 

 Correspondingly, extraordinary growth of any part 

 (hypertrophy) is common. Arrest or suppression is 

 often ascribed to the influence of other organs, but 

 these alleged causes are in few cases supported by ex- 

 perimental evidence. Thus, it is commonly believed 

 that the absence of seeds in the banana and pineapple 

 is due to the excessive development of the flesh in 

 these fruits, but this is a mere conjecture as yet. Some- 

 times spurs and nectarines do not develop. Figs. 2486-7. 



TERATOLOGY 



1783 



2482. One rose growing out of another (on the left). 

 Example of proliferation. 



II. Alteration of Form, involving no considerable 

 change in nature or function of the organs. 



1. fasciation in stems (Fig. 248.'!) produces a broad- 

 ened and fluted form, often curved in crozier-like fash- 

 ion. The apex is furnished with several buds (rarely 



only one), and the arrangement of the leaves is quite 

 anomalous. Fasciation is especially common in rapidly 

 growing steins when an abundant supply of both water 

 and food is available. Asparagus, dandelion and 

 sucker shoots arising from trees after topping or se- 

 vere pruning, frequently furnish examples. Although 

 the fasciated stem seems to have been formed by the 

 early union of several stems, this is rarely the case; 

 rather the growing apex develops extraordinarily in 

 one (transverse) dimension or organizes several buds 

 which grow in unison. 



2. Longitudinal growth in stem parts which normally 

 remain short leads to the unusual separation of the 

 leaves. This is especially noticeable when the floral 

 leaves become thereby more or 

 less widely separated. This is 

 likely to be accompanied by 

 transformation of the floral into 

 green leaves, and sometimes by 

 proliferation. 



3. Unequal growth lengthwise 

 produces apparently twisted 

 steins, with irregular displace- 

 ment of the leaves. Such dis- 

 placement is especially notice- 

 able when it affects whorled 

 leaves, the whorls being 

 stretched out into irregular spi- 

 rals. Unequal growth in two di- 

 mensions by the tissues of a 

 leaf produces the "curly" or 

 erispate leaves, characteristic 

 of many cultivated plants. Fig. 

 1267, Vol. 2. 



4. Local deformities, such as 

 swellings, tubercles and galls 

 of various forms, are usually 

 due directly to the presence of 

 a plant or animal parasite. 

 Fungi, either inhabiting the 

 particular region deformed, or 

 more widely spread through the 

 plant but forming eproductive 

 bodies at the seat of the swell- 

 ing, occasion excessive growth 

 of some or all of the tissues. 

 The "black-knot " on cherry and 

 plum trees, the "plum pockets," 

 the tubercles on the roots of 

 clovers, peas and their kin, are 

 a few out of the hosts of de- 

 formities of this kind, due to 

 plant parasites, and known by 

 various names. 



Many insects, either in the 

 course of feeding on plant 

 juices, or by laying eggs on or 

 in plants, or by reason of the 

 temporary occupation of the 

 part by the larval insect, bring 

 about the formation of galls of 

 various kinds on leaves, stem, or roots. The malforma- 

 tions produced are of the most varied shapes. Sometimes 

 they are merely the production of an unusual number 

 of hairs of special form; sometimes a leaf bulges out 

 at one spot to form a deep pocket or pouch ; sometimes 

 the blade of a leaf is rolled or folded, with or without 

 thickening; all degrees of thickening or outgrowths 

 are produced, from a slight tumor to a perfectly globu- 

 lar apple-gall or even a cylindrical tube-gall ; sometimes 

 a bud has the number of its scales greatly increased to 

 form a cone-like gall; or a flower is distorted until its 

 nature is almost unrecognizable. The variety of form 

 is almost as various as the insects and plants concerned. 

 Indeed, the same insect at different stages of its de- 

 velopment may produce galls of different sorts on the 

 same plant. All orders of true insects except the 

 Orthoptera and Neuroptera may produce galls, but by 

 far the larger number are due to the gall-flies and saw- 

 flies of the order Hymenoptera. The gall-apples of the 

 oaks, the prickly galls of the rose, the irregular brown 

 swellings on canes of the blackberry, and the smooth 

 gall-apples of the willow leaves and twigs are well- 



2483. 



Example of fasciation. 



A branch of Ailanthus 



glandulosus. 



