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Seeds of the laciniated beech gave only 10% of laciniated plants in experiments made by Strasburger; seeds of the monophyllous acacia, Robinia Pseud-Acacia monophylla, were found to be true in only 30% of the seedlings. Varieties have to be freed by selection from all such impurities, since isolation is a means which is quite impracticable under ordinary circumstances.

Fortunately the direct proof of this assertion can be given, and in a case which is narrowly related, and quite parallel to that of the Desmodium, since it affects a plant of the same family. It is the case of the monophyllous variety of the bastard-acacia or Robinia Pseud-Acacia. In a previous lecture we have seen that it originated suddenly in a French nursery in the year 1855.

The "one-leaved" strawberry has already been referred to. It originated from the ordinary type in Norway and at Paris. The walnut likewise, has its monophyllous variety. It was mentioned for the first time as a cultivated tree about 1864, but its origin is unknown.

Other leaves produce one or two small leaflets at the base of the large terminal one, and by this contrivance are seen to be very similar to those of the Desmodium, repeating its chief characters nearly exactly, and only differing somewhat in the relative size of the various parts. Lastly real intermediates are seen between the monophyllous and the pinnate types.

'Barley and wheat come up monophyllous, but peas, beans, and chick peas polyphyllous. Historia plantarum, viii. 1, i. There can be no doubt that here is a piece of minute observation on the behaviour of germinating seeds.

Cytisus prostratus has a variety ciliata, and Solanum Dulcamara, or the bitter-sweet, has a variety called tomentosum. The curious monophyllous variety of the strawberry and many other forms will be discussed later. To enlarge this list it would only be necessary to extract from a flora, or from a catalogue of horticultural plants, the names of the varieties enumerated therein.

These monophyllous varieties are interesting also on account of their continuous but often incomplete reversion to the normal type. Pinnate and palmate leaves are no doubt derivative types. They must have originated from the ordinary simple leaf. The monophylly may therefore be considered as a reversion to a more primitive state and the monophyllous varieties may be called atavistic.

So, for instance, in the case of Sinning, who after sowing the seeds of the common ash, got as large a proportion as 2% of monophyllous trees in a culture of some thousand plants.

The monophyllous bastard-acacia originated in the same way. Its peculiarities will be dealt with on another occasion, but the circumstances of its birth may as well be given here. This was transplanted into the Jardin des Plantes at Paris, where it flowered and bore seeds in 1865.

They were classified by Morren under two heads, according to their formation from one or more leaves. Monophyllous pitchers obey the same law, viz.: that the upper side of the leaf has become the inner side of the pitcher. Only one exception to this rule is known to me.