176 



NA TURE 



[June 21, 1900 



other, which is like the mother in every respect, is looked 

 upon as the product of the nucellus. Mr. Webber's other 

 remarks and illustrations apply to the hybridisation of 

 cotton and maize. 



The structure of Certain Hybrids. — Dr. Wilson con- 

 tents himself chiefly with the external structure of hybrid 

 Passijlora, Albuca., Riiyjs and Bej^o?iia. His figures loring 

 out very forcibly the intermediate nature of many 

 hybrids. The grades between ideal "tuberous" and 

 "non-tuberous" conditions in hybrid Bcoonia are re- 

 markable, joints of the stem falling away in several 

 instances. We reproduce his illustration (Fig. 2), a 



Fig. 2.— Flowering shoot of KiU-s nii^r 

 (nat. size). 



9, X R. grossularia, <J , 



flowering shoot of a hybrid between the gooseberry, $, 

 and black currant, $, and his sections of the ovary 

 walls of the young plant and its two parents (Figs. 3, 

 4, 5). Several experimenters have obtained the cross 

 and fruit from it, but no seeds. It is interesting that no 

 odour of the black currant is possessed by the leaves, and 

 that the caterpillars of the gooseberry saw-fly attack 

 them without hesitation. 



Self-sterility.— \x. is well that the importance of deter- 

 mining whether a plant may not be self-sterile has been 



Fig. 3.— Transverse section of part of the ovarian wall of the black currant. 



brought out by Dr. F. Ludwig. All the individuals of 

 a species which is propagated vegetatively may, in a 

 particular neighbourhood, be practically the same plant, 

 and incapable of fertilising one another (compare the case 

 oi Crocus sativus on p. 276). Hence the importance in 

 bringing pollen from physiologically independent indi- 

 viduals at a distance, mentioned in the discussion by the 

 Rev. G. H. Engleheart with regard to daffodils, but not 

 explained by him. Among a series of his opinions sum- 

 marised conveniently by Dr. Ludwig is one with regard 

 iVO. 1599, VOL. 62] 



to the springing up of races within the same species, which 

 may be self-sterile and self-fertile. Another is of a very 

 practical nature, and deals with the advisability, when 

 mtroducing a new species of plant into a garden, to ob- 

 tain at least two examples of it of as different origin as 

 possible, or to procure the seed of such. 



Work at the Paris Natural History Museum, 1887-99. 

 — M. L. Henry contributes a list of plants supposed ta 

 be hybrids, which he suggests might have their origin 



Transverse sec.ijn of part of the ovarian wall of the hybrid. 



proved by hybridisation experiments. He adds a record 

 of his work during recent years, giving most details with 

 regard to lilacs. 



Grajt Hybrids. — This account of the Bronvaux medlar, 

 by M. E. Jouin, appeared originally in Le Jardin 

 (January 20, 1899) ; and M. Daniel ("La Variation dans 

 la Greff"e," ^«. 6Vz. Nat. Bot. Series 8, vol. viii. (1898), 

 pp. 1-226 ; pis. i.-x.) has figured and given some details in 



Fig. s-— Transver.se section of part of the ovarian wall of the gooseberry. 



his recent paper of the remarkable branches pushed out 

 by the whitethorn stock below the graft. 



Branch No. i is intermediate between the whitethorn 

 and medlar. It is, however, thorny, and bears corymbs 

 of as many as twelve flowers, instead of solitary blossoms. 

 The fruits are medlars, but small and much flattened. 



Branch No. 2. — The young leaves resemble those of 

 the whitethorn ; the older, those of the medlar, being 

 hardly, or not at all, lobed. The flowers are like those of 



