OUR LOCAL FLORA: ITS ECONOMIC ASPECT. 141 
all events not harmful, every unknown cruciferous species is in- 
ferred to be of like quality ; yet in systematic botany the unknown 
species are placed in the order, not by reason of their qualities, 
but because of the ordinal external characteristics of six (four longer 
and two shorter) stamens, four deciduous petals, four deciduous 
sepals; and stamens, petals, and sepals all hypogynous ; that is, 
found on dissection, all to be inserted directly on the flower stalk. 
In the Plymouth Flora we have 39 species of the Cruciferae, in 
Great Britain 66 species ; but throughout the world there are from 
1200 to 1700 species. The discovery of one poisonous Crucifer 
would destroy the sequence and upset our induction. 
Of the 876 plants comprised in the Plymouth Flora we can 
attribute economic value to about 173 only, or say one-fifth; 
101 being marked by Mr. Briggs as common, and 72 as rare. 
Alluding to honey, then or a few weeks since fetching in 
Plymouth 2s. 3d. a quart, chiefly for human food, the lecturer 
said it was an important natural vegetable product, very similar to 
sugar, secreted by flowers in nectaries at the base of their carpels, 
petals, or sepals, and very attractive to insects. Honey partakes 
of the nature of plants whence derived. The honey of the 
Pontine Marshes is poisonous. The honey of commerce obtained 
by bees is never poisonous ; whence we may infer that whatever 
small insects may do, bees neglect, as far as possible, poisonous 
plants. In regard to our local species of the Ranunculus genus of 
plants, most of which are poisonous and have a nectary, it is very 
interesting to observe that R. acris, R. repens, R. bulbosus, R. 
hirsutus, R. arvensis, all being poisonous species, have a conspicuous 
scale over the nectary ; R. Flammula and R. parviflorus, also 
poisonous, have a rudimentary scale over the nectary ; but the 
aquatic species of the genus with no striking properties, and R. 
auricomus and R. Ficaria with good qualities, have no scale over 
the nectary. The scale over the nectary of the poisonous species 
may be a barrier to the proboscis of insects as large as bees. 
The unpleasant odour of the flowers of some poisonous plants, 
such as the Aconitum and Digitalis, would no doubt repel bees. 
Certainly some flowers attract more than others. 
Leaving honey, we may say of plants that Nasturtium officinale, 
common watercress, native, very common by our small streams ; 
the many varieties of Rubus fruticosus, the common bramble or 
blackberry ; Primula vulgaris, the common primrose, which are 
