Walk left down Short Street to the roundabout and cross to the right of it over Maid's Causeway to reach Midsummer Common. Turn right along the pavement - we will enter the common at the cycleway ahead. On your left are two purple-leaved trees (dark green in late summer) which are forms of (18) Norway Maple. Note the opposite leaves with radiating veins characteristic of maples. Norway Maple has similar-sized leaves to Sycamore, but the lobes have marked whiskers (extended narrow tips). As a general rule a purple-leaved tree will either be Copper Beech (usually a large tree with medium-sized oval leaves), Norway Maple, Pissard's Plum (a small tree with small roundish leaves and reddish plums) or Purple Crab (scruffier and sparser leaves soon becoming somewhat greenish).

The next two large trees are fine specimens of (19) Huntingdon Elm, a hybrid elm that is reasonably resistant to Dutch Elm Disease, and which is quite common in Cambridge as a planted tree. Note the asymmetric leaf base, highly characteristic of elms. [N.B. the native elm species, Wych Elm and English Elm, and their intermediate hybrid forms are still very widespread in the UK in hedgerows and as small trees. However they usually die back as soon as the trunk reaches about 10cm in diameter and becomes susceptible to attack by the beetle which carries Dutch Elm Disease].

Turning into the cycleway onto Midsummer Common, the fine mature tree (the first large tree in from the gate) is a (20) Silver Pendent Lime. Silver Lime has a white-felted underleaf which is most apparent when the wind blows, and which makes them much less susceptible to the aphids which attack Common Lime. The pendent form weeps somewhat and has hanging leaves with very long leaf stalks. Silver Lime flowers later than other limes, with overpoweringly strongly-scented flowers and nectar that is apparently toxic to bees.

Ignoring the cycle path, follow the path parallel to the houses past a horse chestnut (there is a better one ahead) and a lime. The next tree is a (21) Tree of Heaven. This is an introduced tree which in places has become an aggressive weed species. The pinnate leaves are alternate and have a characteristic blunt tooth or two at the base of most leaflets. The tree has a distinctive smooth bark with snake-like patterns running up and down, similar to that of the (usually much smaller) snakebark maples. Given the space, this can be a spectacular tall tree with a fine open branch structure - check out another example in All Souls Churchyard opposite Trinity College to see why it is not suitable for the small, or even medium-sized garden!

Beyond the Tree of Heaven is a nice, medium-sized, solo (22) Horse Chestnut (to your left along Victoria Avenue is an avenue mostly comprised of mature Horse Chestnuts). The palmate leaves have flatter leaflets than those of the Red Horse Chestnut we saw earlier, and the buds are sticky. The flower candles look white at a distance but are highly-coloured when seen close to.

And finally, before we cross the treeless prairie to reach Victoria Avenue, the tree just round the corner is a (23) Common Walnut. Although the leaves are alternate and pinnate they are otherwise unlike those of the Black Walnut we saw earlier. The leaflets are untoothed, and most distinctively, the terminal leaflet is much larger than the others. This tree is more common as a garden tree, planted particularly for its nuts which ripen in late autumn.