200 GENETICS [BoT. Absts., Vol. IX, 



montanum.] Hereditas 2: 99-112. S fig. 1921. — Hybrids between species of Epilobium 

 have been reported as occurring among wild plants and are frequently referred to in system- 

 atic literature. In such cases it is difficult to determine, from field observations, what the 

 parent species are in particular cases. Artificially controlled hybrids have been produced 

 between E. hirsutum X E. montanum by Compton. Lehmann has produced hybrids by cross- 

 ing E. parviflorum with 3 other species. Reciprocal crosses were different in a number of 

 characters. When E. -parviflorum was used as female parent the hybrid was quite sterile, 

 no good pollen being produced, while the reciprocal cross produced about 50 per cent good 

 pollen and some mature seed. There were other reciprocal differences. In the Fz generation 

 obtained from E. palustre X E. parviflorum a large range of independently segregating charac- 

 ters was obtained. The author made reciprocal crosses between E. hirsutum and E. mon- 

 tanum. Plants of the parent species were grown simultaneously. At the flowering stage the 

 E. montanum plants were 60-70 cm. tall while the adjacent Fi hybrids were dwarfs, about 

 \-\ as tall and considerably smaller than the smaller parent. The hybrids in other respects 

 were a reproduction of the E. montanum plants, with no evidence of the E. hirsutum parent. 

 The adjacent parent species grew and flowered normally while the dwarf Fi plants failed to 

 produce flowers. Now and then Fi plants more robust than the others appeared, on which the 

 buds reached a higher stage of development than was generally the case. Compton, report- 

 ing on this cross, noted the same peculiarities. The reciprocal cross, E. montanum X E. 

 hirsutum, produced Fi plants of the more vigorous, robust type only. Of the 1919 cultures 

 some of the potted plants were placed in the shade of a tree to prevent too rapid loss of mois- 

 ture. The stems of these plants grew much more rapidly than the remainder left in the open 

 garden. A more nearly normal development ensued and a few flowers opened, on which the 

 petals were larger than those on the parent. Following this, specimens of hybrids and parents 

 were placed in the north window of the laboratory where the hybrids developed much more 

 rapidly than those left in the garden. The flowers opened completely, the petals resembling 

 those of E. hirsutum. In 1920 this experiment was repeated with the same results. The 

 author was unable under these conditions to distinguish reciprocal hybrids. Excessive and 

 scant water supply to shaded plants and to plants in sunlight did not alter the results, indicat- 

 ing that the better development of the shaded hybrids was due to reduced illumination. Back- 

 crosses of these Fi plants to the parents produced abundant seed, which, however, produced 

 only a few seedlings, many of which were weak and soon died as was true of some in the Fj, 

 E. palustre X E. parviflorum, reported by Lehmann. Approximately 100 plants of the back- 

 cross remained alive and showed a large range of variations and character combinations which 

 does not indicate close linkage of genes. Attempts to find a bacterium as the cause for the 

 dwarfing in Fi gave negative results. Results show a distinct difference between the E. 

 montanum X E. hirsutum hybrid produced artificially and the wild form of Epilobium sup- 

 posed to be the field hybrid between these 2 species. — J. L. Collins. 



1291. Alderman, W. H. Experimental work on self-sterility of the apple. Proc. Amer. 

 See. Hort. Sci. 14: 94-101. 1917 [1918].— The investigation was begun in 1912. Previous 

 investigation in apple pollination and sterility consisted mainly in studies of bloom clusters 

 enclosed in paper sacks and, for cross-fertilization, emasculation had usually been practiced. 

 Four possible sources of error enter into such tests: (1) Temperature and humidity conditions 

 within paper sacks are abnormal; (2) individual flowers or clusters of flowers were studied 

 without regard to the remainder of the tree; (3) emasculation may produce a decidedly ab- 

 normal condition; (4) it has not been shown that pollen from other trees of the same variety 

 may not prove effective even though a single flower or single tree is self-sterile within itself. 

 To eliminate these possible sources of error whole trees were enclosed in cheese-cloth or muslin 

 frames. — The temperature was less variable within the muslin-covered frames than without, 

 being 1-2 degrees higher at night and 2-4 degrees lower on bright days; on cloudy days there 

 was very little difference. The humidity was slightly higher within the frames. In a com- 

 parison between muslin-covered frames and paper bags, the latter gave the better results. 

 A summary of 3 years' work with Rome Beauty, York Imperial, and Wagener using pollen from 

 another tree of the same variety shows no advantage over the use of pollen from the same tree. 



