276 BOTANY part i 



vegetable kingdom are, they are in reality but modifications of two 

 different and distinct modes of reproduction. 



The simj)ler of these, or vegp^tative reproduction, consists in 

 the formation of cells or cell-bodies which, after their separation from 

 the parent plant without undergoing any further change, either 

 germinate at once, or develop into new organisms after a period of 

 rest. This mode of reproduction is distinguished as monogenetic, 

 vegetative, or asexual reproduction. 



In SEXUAL REPRODUCTION, the second of the two modes of 

 reproduction, two kinds of reproductive cells, each of which carries 

 the characters of the organism producing it, are first formed, but 

 neither is directly capable of further development, and both j^erish 

 in a very short time, unless opportunity is given for their fusion with 

 each other. Not until the one cell has fused with the other cell does 

 the product acquire the capacity of development and growth. This 

 mode of rejiroduction is termed sexual or digenetic reproduction. 



A. Vegetative Reproduction 



Vegetative reproduction is wide-spread in the vegetable kingdom ; 

 it is completely wanting only in a few plants, such as in many Conifers 

 and some Palms. We shall here exclude from consideration all 

 phenomena of regeneration. Reproduction and increase in number 

 of individuals by means of multicellular bodies (shoots, gemmae) may 

 on purely external grounds be distinguished from a reproduction by 

 single cells (spores, unicellular gemmae). 



Multiplication by Multicellular Vegetative Bodies (Budding-) 

 often consists merely in the separation of lateral shoots, or in the 

 division of a single plant into several. 



In this way the lateral slioots of Azolla, through the death and disruption of 

 the older parts of the parent axis, become separated from one another and continue 

 their growth as independent plants ; similarly, separate plants originate from the 

 vegetative body of the Duckweed {Lemna). 



Multiplication by stolons, rhizomes, and tubers results in a similar formation 

 of independently existing plants. As may be seen in the Strawberry, the Bugle 

 {Ajuga reptans) and numerous other plants, the shoots produced from many of the 

 axillary buds of the widely outstretched stolons take root and form new plants. 

 In cases where the runners themselves eventually die, the parent jjlant becomes 

 finally surrounded by a colony of entirely independent plants. Instead of forming 

 runners, the single tuber niay divide {Corydalis solida), and in this way give rise 

 to two, four, or more new tubers. New bulbs are produced in the leaf-axils of the 

 scales of bulbs, while brood buds (bulbils, gemmae) are frequently developed on 

 aerial vegetative organs. 



Bulbils are found on the inflorescence in the place of the flowers in many species 

 of Allium, in the grass Poa hulhifcra, and also in I'oli/gomcvi viviparum. In 

 Lilium bulbiferuvi, Dentaria bulbifera, etc., the bulbs in the axils of the leaves are 

 specially constructed with a view to detachment from the jiarent plant (Fig. 22). 

 Their swollen leaves contain reserve food material, and frequently devclo}! roots before 



