144 



Gymno- 

 sperms. 



Cycadace*. 



126. Gymnosperms. The ovules are 



naked and not enclosed in an ovary. The pollen grains 

 are thus able to come directly in contact with the micropyle 

 of the ovule. The oophyte developed by the macrospore is 

 represented by a mass of tissue which completely fills the 

 macrospore (embryo sac) and is called endosperm. The 

 oosphere is contained in an archegonium. There is no 

 distinct perianth to the flower. The flowers are unisexual. 

 Cotyledons, two or more, usually appearing above ground 

 on germination, are perennial trees and shrubs, usually resin- 

 ous. Leaves are often acicular. The primary root persists 

 and forms a tap-root. The vascular bundles are open, col- 

 lateral and arranged in a circle round the pith. Secondary 

 growth in thickness takes place by means of a normal cambium 

 ring and the stem consequentlv exhibits a central pith, with 

 distinct bark and wood, while it increases in size by rings of 

 new growth added at the outside of the wood-cylinder and 

 immediately beneath the bark. True vessels are not present 

 in the wood except in that of Gnetaceae. Gymnosperms are 

 sub-divided into the following three orders : 



Cycadacese. 



Conifers. 



Gnetacea3. 



127. Cycadaceae. In this order are 



included the plants which are often seen in Indian 

 gardens and are sometimes wrongly called the Sago Palms. 

 The columnar, usually unbranched, stem with the 

 terminal rosette of large pinnate leaves of these plants 

 gives them a superficial resemblance to the Palms. 

 In India they rarely attain a greater height than 30 feet. 

 The wood is characteristic owing to its possessing alternate 

 layers of woody and bast tissue with no true vessels, and the 

 pith is usually large. The flowers have no perianth and are 

 dioecious. They are situated at, or near, the apex of the 

 stem, the male flower being a cone with a number of thick 

 scales, on the under-surface of each of which are situated 

 numerous pollen-sacs. In the female Cycas tree the charac- 

 teristic macrosporophylls, or carpels, arise on the apex of 

 the main stem, taking the place as it were of the foliage leaves. 

 Although smaller and not green, these carpels somewhat 

 resemble the foliage leaves. The upper portion of the carpel 

 is pinnate, the ovules, w r hich may attain the size of small 

 plums, being borne laterally on the basal portion in the posi- 

 tion of leaflets. Cycas Rumphii, and C. pectinata are well- 



