282 



MacMillax : Observations on Nereocvstis 



hemispherical and now the cells of its central portion are elongated 



in a direction parallel with the axis of the emergence. 



There is 



not any definite development of a central cylinder in the haptere^ 

 but the whole organ is made up of thin-walled somewhat prosen- 

 chymatous cells, covered with the characteristic epidermis, just be- 

 low which the cells are short and flattened and in a state of rapid 

 division concentrically with the surface of the emergence. In the 

 hemispherical stage of the secondar}^ hap'tere the central cells ly-^ 

 ing near the base of the emergence are many of them 150 mic. in 

 length by 45 mic. in breadth, while the cambial cells three or four 



I, 



layers underneath the epidermis are 10 mic. in length and 15 mic. 

 in breadth. 



DicJwtouiy of the sccondmy Hapten's, — The primary hapteres do 

 not commonly show dichotomy, but remain as crcnations of the 



disc-margin. 



As the disc enlarges these crenations sometimes be- 



come indented and this indentation is equivalent to the sharp char- 

 acteristic dichotomy of the secondary hapteres. In the latter 

 after the first emergence has elongated into a cylinder with rounded 

 end, the densely protoplasmic character of the apical region where 

 the cambial cells, or meristcm, is located, gives a darker appear- 

 ancc to the apex of the haptere. Gradually this apex becomes 

 laterally compressed and an indentation appears at the summit 

 separating two meristcmatic areas. Longitudinal sections through 

 such apical areas show that the meristem of the exact apex ceases 

 its active concentric divisions, while right and left of this region 

 the divisions continue, thus forming two new apical cones, which 

 continue to develop as before. Forking of the haptere originating 

 in this manner may be repeated a number of times, and thus the 

 much-branched later hapteres of the plant are developed. The 

 cambial zone of the apex extends do.wn the sides of the haptcric 

 branch and is utilized in the progressive thickening of the organ. 

 The haptere may then be regarded as a conic-cylindrical organ 

 surrounded by an epidermal layer concentrically underneath which 

 is a general cambial zone. By the division of the apical region of 

 this zone the haptere increases in length ; by longitudinal divisions 

 in the lateral portions of the zone the haptere increases in thick- 

 ness. Even in the most mature hapteric branches the lateral 

 ' cambium is still visible as such and I have not been able to dis- 



