OTHER STEMS THREE TYPES OF BUNDLES 26] 



one year old. Stain with hematoxylin. Make a permanent 

 mount. Study with low power, and make a sketch show- 

 ing the shape and Location of the fibro-vascular bundles. 

 Pig. 402. Save the mount for further study. It' meni- 

 spermum stems are nol easily ob- 

 tained, ivy (Hedera helix) or clem- 

 atis may be substituted. 



423. OTHER STEMS. Besides the 

 two types of stems studied above, 

 which are prevalenl among pheno- 

 gams, there are other strucl ares <>i' 

 stems found among the cryptogams. 

 A eommon arrangement of the bun- 

 dles is in the form of a circle some 

 distance from the center, with a few 

 other bundles within the circle. 



Within the circle also are s t imes 



found Large areas of fibrous tissue. 



Pig. 403. There are, however, wide 



variations from this arrangement, 



laii this mode of arrangement is often ci 



typi of stem. 



424. THREE TYPES OF BUNDLES. It ha> ahvad\ been 



said (JIM thai every fibro-vascular bundle is made up of 

 1 wo parts: M) phloem or soft bast} 2 tylem >>v wood. 

 The relative position of these two Btrands of tissue is verj 

 important. There are three plans of arrangement, on 

 which three types of bundles are based. These plans 

 are collateral, concentric, and radial. 



1J.">. In collateral bundles, the phloem and lylem are 

 placed side by side, the sylem being nearer the center 

 of the stem and the phloem outside or nearer the eir 

 cumference of the stem. We find this plan in Ihe stems of 

 phenogams. The collateral bundles maj be either open or 

 closed. < > ] it 1 1 bundles are those which continue to inert 



402. Arrangement of tissues In 



2 year old stem of m 



; pit li ; I . fundamental lis- 

 . epidermis, The Bbro 

 vascular bnndlei an raj 

 prominent. 



sd the f\ i n 



