NOTES AND ABSTKACTS, 



867 



Plant Associations, Bohemian (Beih. Bot. Cent. xvii. pp. 234- 

 240). — Dr. J. Podpera (Olmiitz) points out that the warmth-loving 

 plants of the cretaceous rocks near Prague occur also on basaltic rocks, 

 but not on granites, in North Bohemia. The mosses of the cretaceous 

 rocks (meridional association) are not found on these latter. A large 

 number of sub-alpine species also occur on basalts &c. in the Bohemian 

 " Mittelgebirge," especially on the rock summits, whilst in the Moldau 

 valley they are in more sheltered places. The thermophilous flora 

 consists of elements (1) of meridional character (2) Western, (3) 

 Steppe (north-easterly). The occurrence of these steppe plants on 

 basalt is due to the high annual temperature, small rainfall, the position 

 of these rocks near marshes and open water, to the diathermic and heat- 

 absorbing characters of these open rocks, and of the stony subsoils. 



G. F. S.-E. 



Plant-breeding". By — Fruwirth (Nat. Zeit. Land-Forst. i. pp. 397 

 -404 ; ii. pp. 18-47, 241-253 ; 1903-1904).— Eesults of observations 

 made to obtain information on selection and hybridisation of agricultural 

 plants. Little is known regarding the plants chosen, viz. Eape, Turnips, 

 Cabbage, Mustard, Poppy, Flax, Sunflower, and Camelina sativa. The 

 effects of self-pollination were tested by inclosing single flowers, flowering 

 branches, or single plants in covering of gauze or parchment. Artificial 

 pollination was effected with pollen from the same flower, from another 

 flower on the same plant, and from a flower on a different plant. The 

 fruits and seeds thus obtained were examined as to size, number, and 

 weight of seeds &c. The seeds were afterwards grown to test the merits 

 of the resulting plants. Some of the principal results are as follows : 

 (1) Rape and Turnip : Self-pollination produced seed, but the results 

 were inferior to those from cross-pollination. Hybrids were raised between 

 Rape and Turnip. Seed resulted from the application of pollen from 

 Cabbage on Rape and Turnip, but no mature seed was produced with 

 pollination of Cabbage from the other two. (2) Cabbage : Flowers isolated 

 by covering gave only a few fruits and no seed ; artificially self-pollinated 

 flowers gave only a few poor seeds. Flowering branches covered up gave 

 fewer fruits and seeds than those left uncovered, but the seeds formed were 

 heavier. (3) Mustard : cross-pollination gave the best results ; protected 

 flowers gave seed, but this was inferior to that obtained from unprotected 

 flowers. (4) Flax : inclosing flowers gave results nearly as good as leaving 

 them uncovered. (5) Sunflower : Protected heads formed fruits, but these 

 were barren. Hybridisation of black and white-seeded varieties had no 

 effect ; the seed colour of the mother parent was not influenced. (6) Poppy 

 (Papaver somniferum) : Capsules are always produced even when the stigma 

 has -received no pollen. Protected flowers produced capsules, but only 

 about half of these gave seed. Artificial self-pollination gave better results. 

 Cross-pollination gives the best yield of seed, and heavier seeds. The 

 heaviest capsule on a plant is that on the main axis, and it gives the 

 heaviest seeds ; the capsules of the lower lateral flowers decrease in weight 

 from above downwards, and their seeds are lighter. Crossing takes place 

 between plants growing together, and produces variations in the colour of 

 flower and seed. If single flowers are inclosed in gauze to obtain pure 



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