OECHIDS OF JAMAICA 



Orchids are perennial herbs showing much variety in their 

 habit. They are either terrestrial, growing in the soil, or 

 more or less epiphytic, that is, growing on stems or branches of 

 trees, on rocks, etc., often surrounded by a dense growth of moss. 

 In the simplest form of growth, the stem continually produces 

 new leaves at the apex, while the flowering shoots spring 

 from the axils of older leaves. This method, known as the 

 monopodial, occurs in some epiphytic orchids, as in Dichsea, 

 where the internodes and leaves are both very short. In all 

 terrestrial orchids and many epiphytic, growth of the main axis 

 soon ceases, usually at the end of one season, while a lateral 

 shoot continues the growth next season. The apparent main 

 axis of the plant is then a sympodium, consisting of the basal 

 scale-bearing portions of successive shoots, the upper parts of 

 which are aerial and leafy. The shoots may end in an 

 inflorescence, oi* flowers are borne on special lateral branches. 

 The development of the sympodial rhizome governs the habit 

 of the plant. If the basal portion of the yearly shoot is short, 

 the successive aerial shoots are crowded and the habit is bushy 

 or clustered, whereas if the basal portions are lengthened a 

 creeping or climbing habit results. 



In terrestrial orchids the basal portions of the annual shoots 

 form a thin or fleshy root-bearing rhizome (as in Sjpiranthes), or 

 a tuber is produced each year (as in Hdbenaria, Bletia). The 

 aerial stem is slender, bearing one to many foliage-leaves and 

 ending in a single flower or an inflorescence. The leaves are 

 inserted along the stem (cauline) or are clustered at the base 

 (radical). 



The majority of epiphytic sympodial forms are pseudo- 

 bulbous ; that is, the stem is thickened to serve as a reservoir 

 of food and water. The pseudobulb consists of only one 

 internode and bears one or more leaves at its apex, or of several 

 internodes and bears leaves throughout its length, or bears 

 scales at the lower nodes and a terminal tuft of leaves. The 



