SUNFLOWER APICAL BUD 47 



compare the older stem, where the protoplasmic contents are 

 replaced by air. 



Note on Interfascicular Cambium, It has been seen that in 

 the Sunflower the bundles are quite separate in the young stem, 

 being isolated by masses of quiescent ground tissue. Later, 

 the cells of the latter tissue begin to divide actively as an inter- 

 fascicuiar cambium layer, lying between the originally separate 

 bundles. This interfascicular cambium joins the margins of 

 the fascicular cambium, and a complete cambial cylinder is 

 thus formed. But here in the Sunflower, as in most herbaceous 

 annual plants, the interfascicular cambium is not very long 

 active, the product of its activity being but a narrow band of 

 secondary fascicular tissue : the identity of the original bundles 

 can thus be recognized at a glance. These points can be very 

 well observed in the stem of Ritinus and other herbaceous or 

 semi-herbaceous Dicotyledons. (Compare Fig. 2, A, B.) 



* * * Apical Bud. 



V. Take the apical bud of a young plant, or of a young lateral 

 branch of the Sunflower, and cut longitudinal median sections ; 

 treat with potash, and mount in glycerine : a better method is 

 to treat with " eau de javelle," and mount as directed on p. 32 : 

 examine with a low power, and then observe 



1. That the axis ends in a naked, broadly-conical apex 

 {punctum ves;etationis), which is surrounded and enveloped 

 by- 



2. Leaves : these may be observed in various stages of 

 development, the youngest being nearest to the apex : their 

 order of development is thus acropetal. The surfaces of the 

 older leaves are covered with 



3. Hairs, which are absent from the apical cone and the 

 youngest leaves, the hairs being developed subsequently to the 

 leaves themselves. 



Note (with a high power) that the apical cone itself consists 

 of thin-walled cells with plentiful protoplasm, which are smaller 

 than the cells of the mature tissues already studied, and are in 

 a state of active division, i.e. they are merismatic. Observe 



