STEMS, BULBS AND BUDS 



43 



Formation of Buds. — In most plants the buds undergo a 

 period of rest. In our temperate climates they are usually 

 forming during one growing season and rest until the next. 

 These buds are so well developed during the formative period 

 that each is practically a complete leafy shoot or flower in mini- 



FlG. 21. — Lilac bud showing transition from scales to leaves. Also showing that the apical 

 bud has been winter-killed and the next two lateral buds developed. 



ature. Therefore, their opening and growth during the next 

 growing season is extremely rapid. 



Structure. — An examination of the structure of stems shows 

 two types: the dicotyledonous and the monocotyledonous (Figs. 

 22 and 23). In the former we find the fibro-vascular bundles 

 an'anged in a circle, while in the latter we find them, scattered 

 throughout a pithy tissue or arranged in a circle about a hollow 

 center. However, the true difference between these two types of 

 stems depeoads on the structure of the fibro-vascular bundles. 



Structure of the Dicolytedonous Stem. — A cross-section of a 



