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varieties. Not a few plants contained in smaller collections, 
are still ■wanting in the greater herbariums Tvhich are supposed 
to be general or complete. Dr. Klotzseh estimates the present 
entire number of phoenogamous plants in the gi'eat Royal Her- 
barium at Schoneberg, near Berlin, of ^Thich he is the curator, 
at 74,000 species. 
Loudon's useful ■work, Hortus Britannicus, gives an approxi- 
mate "View of all the species which are, or at no remote time 
have been, cultivated in Bi'itish gardens : the edition of 1832 
en^lmerates, including indigenous plants, exactly 2G,660 phseno- 
gamous species. "We must not confound with this large number 
of plants which have grown or been cxiltivated at any time and 
in any part of the whole British Islands, the number of living 
plants ■which can be shown at any single moment of time in any 
single botanic garden. In this last-named respect the Botanic 
Garden of Berlin has long been regarded as one of the richest in 
Europe. The fame of its extraordinai-y riches rested formerly 
only on uncertain and approximate estimations, and, as my 
fellow-labourer and friend of many years' standing, Professor 
Kunth, has justly remarked (in manuscript notices communi- 
cated to the Gartenbau-Yercin in December, 1846), 'no real 
enumeration or computation could be made until a systematic 
catalogue, based on a rigorous examination of species, had been 
prepared. Such an enumeration has given rather above 14,060 
species ; if vre deduct fi'om this number 37o cultivated Ferns, -we 
have remaining 13,685 phEenogamous species ; among ^hich -we 
find 1,600 Compositse, 1,150 Legxmiinosae, 423 Labiatee, 370 
TJmbelliferae, 460 Orehidere, 60 Palms, and GOO Grasses and 
Cyperacece. If vre compare ■with these numbers those of the 
species already described in recent works, — Compositse (Decan- 
dolle and Walpers) about 10,000 ; Leguminosae, 8,070; Labiatfe, 
(Bentham), 2,190; Umbellifer^, 1,620 ; Grasses, 3,544; and 
Cyperacete (Kunth. Enumeratio Plantarum), 2,000; — we shall 
perceive that the Berlin Botanic Garden cultivates, of the very 
large families, Compositie, Leguminosa?, and Grasses, only l-7th, 
l-8th, and l-9th ; — and of the small families, Labiatae and 
Umbelliferee, about l-5th or l-4th, of described species. If, 
then, "we estimate the number of all the different phaenogamous 
plants, cultivated at one time in all the botanic gardens of 
Europe at 20,000, "we find that the cultivated species appear to be 
about the eighth part of those -which are already either described 
or preserved in berbarixuns, and that these must nearly amount 
to 160,000. This estimate need not be thought excessive, since 
of many of the larger families, (for example, Guttiferse, Malpi- 
ghiacece, Melastomeas, Slyrtaceoe, and KubiacesE), hardly a 
hundredth part are found in oiu" garden.' If -we take the number 
given by Loudon, in his Hortus Britannicus, (26,660 species,) as 
a basis, we shall find— according to the justly drawn succession 
of inferences of Professor Kunth, in the manuscript notices 
from which I have borrowed the above— the estimate of 160,000 
species rise to 213,000 ; and even this is still very moderate, for 
Heynhold's Nomenclator botanicus Hortensis (1846) even rates 
the phaenogamous species then cultivated at 35,600 ; whereas I 
have employed Loudon's number for 1832, %'iz., 26,660. On the 
■whole, it would appear fi'om "what has been said,— and the con- 
clusion is at first sight a sufficiently striking one — ^that at present 
there are almost more known species of phasnogamous plants 
(with which we are acquainted by gardens, descriptions, or 
herbariums), than there are known insects." 
" If these considerations have led us to the proportion borne 
by the species of plants cultivated in gardens to the entire 
amount of those which are already either described or preserved 
in herbariums, we have still to consider the proportion borne by 
the latter to what we conjecture to be the whole number of 
forms existing upon the earth at the present time, /. e. to test 
the assimied minimum of such fonns by the relative numbers 
of species in the different families, therefore, by uncertain 
multipliers. Such a test, however, gives for the lowest limit or 
minimum number results so low as to lead us to perceive that 
even in the gi'eat families,— our knowledge of which has been 
of late most sti'ikingly enriched by the descriptions of botanists, 
— we are still acquainted with only a small part of existing 
plants. The Eepertorium of Walpers completes DecandoUe's 
Prodromus of 1825 up to 1846 ; we find in it, in the family of 
Leguminosae, 8,068 species. AVe may assume the ratio, or rela- 
tive numerical proportion of this family to all phEenogamous 
plants, to be l-21th— as we find it 1-lOth within the tropics, l-16th 
in the middle temperate, and l-33rd in the cold northern zone. 
The described Leguminosae would thus lead us to assume only 
169,400 existing phcenogamous species on the whole surface of 
the earth, whereas, as we have shown, the Compositfe indicate 
more than 160,000 already known species. The discordance is 
instructive, and may be further elucidated and illustrated by 
the foUo^wing analogous considerations. 
The major part of the Compositee, of which LinniEus knew 
only 785 species, and which has now £;rowri to 12,000, appear to 
belong to the Old Continent ; at least Decandolle described only 
3,590 American, whilst the European, Asiatic, and African 
species amounted to 5,093. This apparent richness in Composittn 
is, however, illusive, and considerable only in appearance ; the 
ratio or quotient of the family, l-15th between the tropics, l-7th 
in the temperate zone ; and l-13th in the cold zone, shows that 
even more species of Compositse than Leguminosa must hitherto 
have escaped the reseai-ches of travellers ; for a midtipUcation 
by 12 would give us only the improbably low number of 144,000 
phaenogamous species. The families of Grasses and CyperacetB 
give still lower results, because comparatively still fewer of their 
species have been described and collected. We have only to 
cast our eyes on the map of South Amei'ica, remembering the 
Avide extent of territory occupied by gi-assy plains, not only in 
Venezuela and on the banks of the Apure and the Meta, but also 
to the south of the forest-covered regions of the Amazons, in 
Chaco, Eastern Tucuman, and the Pampas of Buenos Ayi'es and 
Patagonia, bearing in mind that of all these extensive regions 
the greater part have never been explored by botanists, and the 
remainder only imperfectly and incompletely so. Northern and 
Central Asia offer an almost equal extent of Steppes, but in 
which, however, dicotyledonous herbaceous plants are more 
largely mingled with the GramineEe. If we had sufficient 
grounds for believing that we are now acquainted with half the 
phtenogamous plants on the globe, and if we took the number 
of known species only of one or other of the before-mentioned 
numbers of 160,000 or 213,000, we should still have to take the 
number of grasses (the general proportion of which appears to 
be I-12th), in the first case at least at 26,000, and in the second 
case at 35,000 different species, which would give respectively in 
the two cases only either l-8th or 1-lOth part aslinown. 
"The assumption that we already know half the existing 
species of phEenogamous plants is farther opposed by the follow- 
ing considerations. Several thousand species of MonocotyFedons 
and Dicotyledons, and among them tall trees, — I refer here to 
my o'wn Expedition, — have been discovered in regions, consider- 
able portions of which had been previously examined by dis- 
tinguished botanists. The portions of the great continents 
which have never even been ti'odden by botanical obsen'ers, 
considerably exceed in area those which have been traversed by 
such travellers, even iu a supei-ficial manner. The greatest 
variety of phaenogamous vegetation, /. e., the greatest number of 
species on a given area, is found between the tropics, and in 
the sub-tropical zones. This last-mentioned consideration 
renders it so much the more important to remember how almost 
entii-ely unacquainted we are, on the New Continent, north of 
the equator, with the Floras of Oaxaea, Yucatan, Guatimala, 
Nicaragua, the Isthmus of Panama, Choco, Antioquia, and the 
Provincia de los Pastos; and south of the equator, with the 
Floras of the vast forest region between the Ucayale, the Hio de 
la Madera, and the Tocantin (three great tributaries of the 
Amazons), and with those of Paraguay and the Provincia de los 
Missiones. In Africa, except in respect to the coasts, we know 
notliing of the vegetation from 15 deg. north, to 20 deg, south 
latitude ; in Asia we ai'e unacquainted "^ith the Floras of the 
south and south-east of Arabia, where the highlands rise to 
about 6,400 English feet above the level of the sea,— of the 
coimti'ies between the Thian-schan, the Kuenltin, and the Hi- 
malaya, all the west part of China, and the gi-eater part of the 
countries beyond the Ganges. Still more unkno^-n to the 
botanist are the interior of Borneo, New Guinea, and part of 
Australia. Farther to the south the number of species under- 
goes a wonderful diminution, as Joseph Hooker has well and 
ably shown from his own observation in his Antartic Flora. 
The three islands of which New Zealand consists extend from 
34A deg. to 47:}: deg. S. latitude, and as they contain, moreover, 
snowy mountains of above 8,850 English feet elevation, they 
must include considerable diversity of climate. The Northern 
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