A more elaborate account of the experiments will be found in several numbers of the ‘Botanische Zeitung,’ and the author expresses his final results in the following words (see Bot. Zeit. 1887, p. 773):—‘These experiments prove with certainty (1) that insufficient nutrition may cause considerable morphological changes (viz. qualitative variations) which are in the first place acquired by the sexual apparatus of the flower, (2) that the “transient” (Weismann) characters acquired by the individual can be transmitted[[289]].’

The data upon which Hoffman bases these opinions are certain experiments conducted upon various plants, in order to determine the conditions of life under which abnormal flowers or any other variations occur most frequently: to decide, in short, how far variations are caused by the change of conditions.

It is obvious that the attention of the author was not at first directed to the question of the transmission of acquired characters. His experiments are of a much older date than the present condition and significance of the question before us. Hoffmann has, in fact, re-examined his former results from the new point of view, and this explains why his proofs are not always sufficiently convincing when applied to the present issue. But this is of no great importance, inasmuch as there is no necessity for me to question the correctness of his assumptions.

The essential details of the experiments to which he directs attention are as follows.

Different plants with normal flowers were subjected to greatly changed conditions of life for a series of generations. They were, for example, crowded together in small pots. Under these circumstances the plants were of course poorly nourished, and in the course of generations, several species produced a variable proportion of abnormal—viz. double-flowers. This, however, was not always the case, for such flowers did not appear in Matthiola annua and Helianthemum polifolium. In other species, such as Nigella damascena, Papaver alpinum and Tagetes patula, they appeared and often increased in numbers in the course of generations, although this was not a constant result. For instance, four successive generations of Nigella damascena, when closely sown, produced the following results:—

1883.No double flowers.
1884.No double flowers.
1885.23 typical flowers:6 double flowers.
1886.10 typical flowers:1 double flower.

But it was not always the case that the double flowers continued to appear after they had been once produced. In Papaver alpinum, which Hoffman has cultivated in successive generations since 1862, other changes in addition to the doubling of the flowers first appeared in 1882, viz. a slight variability in the form of the leaf, and a greater variability in the colours of the flowers. The production of double flowers appeared to be favoured by poor nutrition caused by crowding the plants. The results as regards the number of double flowers produced in this species by close sowing, from 1882-1886, have been as follows:—

Experiment XI.1881.40per cent. of double flowers.
1882.4per cent. of double flowers.
1883.5·3per cent. of double flowers.
Experiment XVII.1884.13·per cent. of double flowers.
1885.0·0per cent. of double flowers.
1886.0·0per cent. of double flowers.

Although in these and some other series of generations the double flowers again disappeared in the later generations, yet there can be hardly any doubt that their first appearance was due to the abnormal conditions of nutrition. This conclusion is also unaffected by the fact that double flowers appeared in nearly the same proportions in consequence of cultivation in ordinary garden soil. The plants which were crowded in pots produced 2879 normal flowers, and 256 (=8·8 per cent.) abnormal and mostly double ones, while 867 normal and 62 (=7·0 per cent.) abnormal ones were produced on garden beds. Hoffman will not indeed admit that such a comparison can be fairly made, for the plants in the garden beds were raised from seed which was in part taken from the double flowers, and was therefore, he believed, under a strong hereditary influence. But this latter assumption is not supported by the results of his own experiments.

Thus experiment XVIII., conducted upon Papaver alpinum, is described in these words,—‘Seeds yielded by double flowers from experiment XI. (1883), were sown in pots, and the resulting plants produced from 1884-1886, fifty-three single flowers and no double ones.’