GENERAL REQUIREMENTS. 7 



covering of old leaf bases adds to the strength of the trunk, and 

 is a protection of the tissues within it from the excessive heat to 

 which the plant must be exposed in order to enable it to ripen 

 its fruits properly. 



4. The stem is surmounted by a large terminal bud, from 

 which fresh young leaves are continually being 

 developed to replace the older leaves that are 

 withering up. Full-grown leaves are usually 9 to 17 feet long. 

 They may be described as feather-shaped ; each leaf having a 

 long tough main axis and a large number of narrow leaflets, 

 arranged along either side of it like the pinnae of a feather. 

 Collectively these pinnae give far less resistance to winds than 

 a single large undivided leaf blade would have done, and there 

 is, therefore, less risk of the tree being overthrown, or its stem 

 broken during a wind storm. Instead of the pinnae being 

 arranged in one plane on either side of the main axis as in the 

 case of the pinnae of a feather, they are usually arranged in two, 

 and sometimes three or more, more or less distinct planes on either 

 side of it (see illustration No. 8, page 6c). This arrangement 

 also facilitates the passage of the wind between the leaflets. 

 The edges of the base of the main axis of the leaf for about 

 | feet up its length are extended into a thin wall of soft tissue 

 which in the bud forms a cylinder completely encircling all the 

 younger leaves (see illustration No. 9, page 6d). TKej w^lT'-Jf 

 this cylinder or leaf -sheath is composed of a close- 'network- , . ;^ ;-; : . 

 long interwoven tough sclerenchymatous fibres and sap -conduct-' 

 ing tissues lying in a matrix of soft walled cells. As each leaf- 

 base is provided with this sort of sheath and the apical bud of 

 the palm is composed of a series of leaves, the sheaths of which 

 each envelope the younger ones, the undeveloped leaves are 

 protected in their youngest and most tender stage in a series of 

 cylinders fitted over each other like the sections of a nearly 

 closed telescope. 



With the development of the younger leaves in the bud, 

 the sheaths at the bases of the older leaf-stalks become stretched 

 wider and wider to accommodate them, eventually being split 



