ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 809 



lobes must rather be compared to the " ovular mamelon " in angio- 

 sperms. The sporaugifcrous lobe, bearing the nucellus and the 

 integuments, may be regarded as presenting the transition from the 

 sporangium of Opliioglossum to the ovule of angiosperms. 



Although the Cycadeee are undoubtedly the most ancient phanero- 

 gams, and the most nearly allied to cryptogams, M. Treub does not 

 consider it probable that any existing gymnosperms represent the 

 actual transition from cryptogams to angiosperms ; the forms we now 

 have are probably derived from those which actually constituted the 

 connecting link. 



Cell- and Nuclear Division in the Formation of the Pollen of 

 Hemerocallis fulva.* — According to E. Tangl, the young pollen 

 mother-cells of Hemerocallis fulva have comparatively large finely 

 granular nuclei, containing several nucleoli which are distinctly 

 coloured by methyl-green or Beale's carmine. At a later period the 

 number of nucleoli diminishes, so that each nucleus has only one or 

 less often two, which are no longer coloured by methyl-green, while 

 their colouring by Beale's carmine remains unchanged. At the same 

 time the originally regular distribution of the granules is altered. 

 They at first form a network, and afterwards a thin layer on the wall 

 of the nucleus, with a larger central group, and an anastomosing net- 

 work between them. To the hyaline substance between the granules 

 Tangl applies Flemming's term, " intermediate substance." At this 

 stage the structure of the nucleus is completely destroyed by alcohol ; 

 by treatment with acetic acid and methyl-green the granules are 

 coloured a dark blue-green. At a later period the regularly distri- 

 buted small granules of the nucleus are replaced by larger granular 

 structures which behave in the same way towards reagents. Subse- 

 quently the nuclear membrane disappears, and the intermediate 

 substance assumes a granular character, exactly resembling that of 

 the surrounding protoplasm. This is followed by a new nucleus of 

 irregular outline, destitute of membrane, and nearly entirely composed 

 of granular substance which takes the pigment, and which is probably 

 derived genetically from a coalescence of the granular structures with 

 the nucleolus of the earlier nucleus. If two nucleoli are originally 

 present, one of them appears not to take part in this coalescence, but to 

 remain imbedded in the protoplasm. From the new nucleus is formed 

 the nuclear plate, consisting in most cases of granules somewhat 

 elongated in the direction of the axis of the spindle, less often of a 

 continuous disk with teeth directed towards the pole, and lying in a 

 clear hyaline portion of the protoplasm. The daughter-nuclei are at 

 first roundish and finely granular ; they subsequently change their 

 form from unequal growth, their contents becoming at the same time 

 differentiated into granules, intermediate substance, and membrane. 

 The granules afterwards all lie on the membrane, on which they form 

 a network with polygonal meshes. The formation of the nuclear 

 plates in the secondary nuclei is preceded by a considerable diminu- 



* Denksehr. K.K. Akad. Wiss. (Wieu), xlv. (1S82) 22 pp. (4 pis.). See Bot. 

 Centralb]., xi. (1882) p. 169. 



