Notes. 
663 
none which can be reasonably regarded as angiospermous plants. If 
we compare the Wealden flora with that of the preceding Jurassic 
epoch, and again with the flora of overlying beds, we find in the 
former case a very striking similarity, and in the latter an almost 
equally well-marked difference. In short, the Wealden vegetation 
seems to be of essentially the same character as that which is so well 
represented in the Jurassic rock of the Yorkshire cliffs. Questions 
of climate and geographical distribution are of considerable interest 
when we are dealing with geological floras, but speculations as to 
climatal conditions are as a rule far from satisfactory when the 
evidence is furnished by extinct species. So far as it is possible to 
draw any conclusions of scientific value, our extended knowledge of 
Wealden plants supports the view of more or less tropical conditions 
of growth. A detailed comparison of the English species with those 
from other parts of the world, shows very clearly an exceedingly wide 
distribution of some characteristic forms, and points to a distinct 
uniformity in the vegetation of this period in widely separated regions. 
As points of some botanical interest, brought out by an examination 
of the English plants, mention may be made of the evidence obtained in 
support of the generic identity of Williamsonia and Bennettites , and the 
discovery of fertile pinnae in Sphenopteris Mantelli and other ferns; but 
limits of space preclude any discussion on these and other matters of 
greater or less botanical importance. A. C. SEWARD, Cambridge. 
THE NUCLEI OF LILIUM LONGIFLORUM.— If the chromo- 
somes of the dividing nuclei in the growing-point of the stem of this 
Lily are counted, it is found that their number is variable ; thus 
nuclei with sixteen or twenty-four chromosomes are the most usual, 
and of these the former number is the most frequent. Besides these 
nuclei there are others which very probably contain intermediate 
numbers, e. g. eighteen, twenty, twenty-two. Again, in the divisions 
taking place in the pollen-mother-cells and in the upper nuclei of the 
embryo-sac a variation occurs. Some pollen-mother-cells contain 
nuclei with eight, others with twelve or ten chromosomes and that too 
in the same pollen-sac. In the upper nuclei of the embryo-sac eight, 
ten, or twelve chromosomes are found. 
Before entering on the early stages of karyokinesis, the nucleus of 
the pollen-mother-cells of this plant possesses a very delicate and 
complexly coiled nuclear thread. Portions of this thread lie parallel 
