This is the second edition of a book that I remember buying back in the eighties and is promoted as a serious field guide for the serious botanist. Clare O’Reilly who has revised and updated the book says
‘For 25 years this book has reigned supreme as the most useful field guide to British and Irish wild plants. No other field guide has full botanical keys as well as colour illustrations’(Rose 2006) page 6
The introduction has a very good ‘how to use this book’ section including a clear guide as to how keys work. Unlike the Streeter book this book is about flowering plants but not grasses and sedges or ferns. There are no non native conifers although these are widely planted.
The first key is called the master key and enables you to find the plant families. For my plant the first question is whether the plant has flowers or not, this is because the book features a key to plants not in flower. Presuming that I have a flower the next choice is whether the flower is a dense collection of flowers like a dandelion or whether it has individual flowers. I went for the second option and this takes me to whether or not the flowers are structured in umbels which I think it does.
The key then leads the reader to categories labelled A-P. My category E soon leads to Euphorbiaceae which is the correct one.
As with Streeter the key for the spurge family begins with a brief description of their common characteristics. Immediately below the introduction is a section called ID tips which tells me exactly what features to look for when using the key. In this case I need to look for
1 Structure of the flowers
2 Shape of the glands around the flower
3 Shape of the leaves and whether stalked
4 Whether fruits have warts on them and what they look like
There is also a very useful diagram and definition of umbel bracts and upper bracts.
All this is excellent stuff but the first question in the key is whether the leaves are opposite or alternate and as they appear opposite the key does not work, I end up identifying the plant as E peplis or E lathyris.
If I accept that the leaves are alternate then the key does however work, although the issue remains around opposite or alternate leaves with both books. I decided to look at Stace (1997) and the key here is more accurate because it asks if the leaves are alternate on the main stem implying that other stems may have opposite leaves. so I got there in the end the plant is Petty Spurge Euphorbia peplus.