of the stigma, upon which Kadlkofer places so much reliance, as proving the fact of non-impregnation, a figture is given (after Nees) of the young fruit still surmounted, by the perfect stigma; and it is stated that the stigma is not only persistent, but even increased in growth after impregnation—a circumstance which (it is added) has often been observed by Klotzsch in the Euphorbiaceæ.
Experiments upon Spinacia oleracea, similar to those just mentioned upon Mercurialis, led the author to the conclusion that Spinacia is, in point of fact, an hermaphrodite plant, which can produce no perfect seeds when impregnation is really prevented, but that such prevention is a most difficult task, it being next to impossible to remove the male flowers at so early a stage and with so much care, as to be certain that impregnation has not taken place.
Lastly, Regel entered upon the same investigations with female plants of Cannabis saliva. He cut the plants down to a few branches, so that he might be able to examine with a lens the numerous flowers which were daily produced, and so that the whole vegetative force of the plant might be directed to those few branches, and thus favour the formation of fruit. He kept these plants in favourable situations until the month of October, up to which time none of the ovaries produced seeds; but all of them, without exception, withered and dropped off. He then put these plants, and another female plant subsequently reared, but not cut down like the former, into a room with a male plant. The heat of the room and other circumstances he considered to be unfavourable to fructification. Nevertheless, the female plants which had been cut down produced and ripened seed, whilst the other female plant did not fructify. The results are thus recapitulated by the author.—Two plants cut down so that the whole vegetative power was directed to the formation of seeds, placed under favourable circumstances, vigorous in their growth, and having daily access to fresh air, produced no fruit so long as impregnation was withheld. The same plants under unfavourable circumstances, in a close hot room, and when the days were shortened, produced and ripened seeds as soon as they were subjected to impregnation. A plant not cut down like the above, and impregnated under the (unfavourable) circumstances just mentioned, produced no seeds.
Regel states that he has not had the opportunity of examining Cœlebogyne, and can therefore give no decided opinion as to that plant. He suggests the possibility of the future discovery of sessile anthers between the bracts or near the glands, or that individual pollen-grains may be developed in the interior of the embryo the latter suggestion arising from the fact of Deecke having seen in Cœlebogyne a pollen-tube which had penetrated to the embryo-sac, although neither he nor Radlkofer could discover pollen-grains upon the stigma.
Since the publication of Regel's paper, Dr. Braun has returned to the subject in a communication made to the Berlin Academy, and published in their Transactions for 1859. This essay, which has
