correct, as De Candolle supposes, to say that this group never pro- 
duces true leaves, since they are sometimes very distinctly formed on 
young shoots of Cactus speciosus, though they soon fall off. 
Popu.ar anp GeocrapuicaL Notice. This plant is evidently 
most closely allied to Cactus speciosissimus, var. lateritius, figured 
in No. 1596 of the Botanical Register; but no detailsare given with 
that figure, and it is merely referred to as a hybrid. Whether the pre- 
sent plant be a hybrid, or merely an extraordinary variety of Cactus 
speciosus, is involved in some degree of uncertainty. It was raised in 
the Botanic Garden at Cambridge, with 23 others, from seeds of Cac- 
tus speciosus, sown in the year 1828. The person who raised these 
plants (Wm. Scott) feels convinced that there was no specimen 
of Cactus speciosissimus in the garden at that time, by which the hy- 
bridity could have been produced; but in the absence of any precise 
record it must remain very doubtful whether his statement can be trust- 
ed. How many interesting facts are daily lost to science by the want 
of sufficiently accurate details respecting the numerous varieties and 
hybrids which the practical gardener is continually producing; and 
how desirable it would be for such persons always to record the exact 
circumstances under which their experiments are conducted. We might 
then hope to secure sufficient data for unravelling much of that mys- 
tery which at present hangs over our subject, especially as regards the 
identification of species ; and so obtain some sound knowledge of the 
laws upon which the variation of different individuals from a particular 
type depends. The close resemblance which Cactus speciosissimus la- 
teritius bears to Cactus Jenkensonii is noticed in the Botanical Regis- 
ter, and the flowers of the present plant also appear to differ from it 
chiefly in their deeper colour, (not paler as in that variety). It excels 
the Jenkensonii in having the segments of the perianth more connivent, 
and the whole flower stands out horizontally, and does not droop as in 
that species. InJ enkensonii the anthers and stigmas are purplish, but 
we possess a seedling from this species where several of these trifling 
distinctions are less marked, and where none but the eye of the horti- 
cultural amateur would be inclined to recognize much difference be- 
tween it and the present plant, always excepting the herbage, since the 
stems of Jenkensonii are all flat and less fleshy. 
The irritability exhibited by the leaves of the Sensitive plant is a 
phenomenon with which most persons are familiar; and many of our 
readers have probably also witnessed the effect produced by touching 
