Praeger's classic 1932 work provides a systematic description of the Sempervivum-group (Crassulaceae) in order to resolve the confused state of Sempervivum in our gardens and horticultural books.

Sempervivums (Hauswurz, houseleeks, liveforever, hen and chicks) found in gardens are often hybrids. They occur from the Canary Islands to Great Britain to the Himalaya.

Where species are so variable and hybridization is so rampant as in the Sempervivum-Group, only prolonged field-work and cultivation will lead to reliable results. In the present instance, by growing all the plants for at least several years under similar and uniform conditions, and observing them at all seasons, the author presents an account of the group in which, he hopes, error has been reduced to a minimum.

The first part of the book provides a general introduction to systematics, history, variability, hybrids, parasites, epiphytes, teratology, cultivation, economics and hardy Sempervivums in gardens.
The systematic second part provides descriptions and illustrations of Sempervivum, Aichryson, Aeonium, Greenovia and Monanthes of the Sempervivum-Group.

An addendum with garden names and an index with species and synonym names complete the volume.

Praeger’s classic work of 1932 provides a systematic description of the Sempervivum group (Crassulaceae). This reprint has been done from the 1967 reprint where the author’s name is stated as L R Praeger. However the original 1932 edition published by The Royal Horticultural Society clearly shows the author’s name as R Lloyd Praeger and this is of course, the correct name. This unfortunate error however does not deter from the contents.

The book is in two parts. The first part provides a general introduction to the systematics and history of the group as well as looking at variability and hybrids, cultivation and hardiness in gardens, and even economic uses (very few).

The second part is the ‘meat’ of the book and provides descriptions and illustrations (detailed black and white line drawings) of the plants in the Sempervivum group, namely Sempervivum, Aichryson, Aeonium, Greenovia and Monanthes.

An addendum with garden names and an index with species names and synonyms complete the volume.

If you do not have the original or the 1967 reprint, then this high quality hardback edition is well worth buying if you have an interest in this group of plants. This is a classic monograph on the group and the original is now a collectors’ item, especially if in good condition.

CactusWorld Vol. 30 (2)

The re-issue of this classical work after 80 years would seem rather astonishing before turning over its pages. Focusing to the genera Sempervivum, Aichryson, Aeonium, Greenovia, and Monanthes, it exhibits some peculiarities which might be still of interest for the present botanical research.

This monograph was written in a very practical scope, using broad comparisons between field and garden observations, discussing the frequent identification problems, especially exemplified by the hardy Sempervivum species (p. 26), and even going into great detail about horticultural questions (unfortunately without any precise cultivation schedule, including temperature, moisture, etc.). This approach is sensible also in the book format as well as in the concise author’s style and in the numerous, self-explanatory and fine pictures (almost all the taxa were skilfully drawn in vivo by Eileen Barnes, an artist from the National Museum of Dublin).

The work is merely divided in three parts: a short general introduction (p. 1-33) emphasizing all biological features, a systematic treatment (p. 34-244), and a file of the excluded species and doubtful names (p. 245-254), completed by lists of garden and scientific names (p. 255-265).

This impressive and fairly thorough monograph bears yet the stamp of its time by some weaknesses: it provided several relevant data e.g. about parasites, epiphytes (mainly lichens) and teratology, but no information about the phytosociological context and no more about the root system, the soil pattern, or the branching and thickening of stems, all features however closely related to horticultural concerns. As expected, there are no chromosome study (highly complex in this group, but useful for analysing the putative hybrids), and no remarks about the conservation in the nature.

This book reminds us at the right time the study of living plants on the field, prolonged by cultivation in garden and greenhouse, is yet the most reliable source for a first understanding of the groups whose some or all members are poorly preserved in herbaria, such as succulent plants, and which exhibit often a broad herbarium sheet was cited (except when it was the only available material), although a detailed nomenclature was given below each taxon, and we may be surprised too no reference was done to any spirit collection, but no anatomical study was undertaken or even cited.

Currently many intermediate taxonomic ranks (sectio, varietas, forma) are ascribable. Many taxa previously described as good species are now transferred into notho-species or sub-species, such as recalled by Gérard Dumont in his indispensable website dedicated to the genus Sempervivum: Sempervivophilia (http://sempervivophilia.stalikez.info/).

The increasingly splitting botanists / gardeners relationships should recover their nobleness through a new gathering of skills. In addition, it is quite clear that the classical typification after few specimens or even a single one is a severe hindrance, constraining any useful comparison between protologues and features range observed in Sempervivum populations (in situ and ex situ). This monograph basic work for the study of the group and reprinted in 2012 raises the role that should play the ex situ observations for understanding groups of plants that cannot be kept well in a herbarium.

Jérémy Tritz, (Neuchâtel)

ADANSONIA sér. 3, 2013, 35 (2), page 391-392