362 PLANTS STERILE WITHOUT INSECT-AID. CHAP. X. 



this was a false appearance ; 60 heads on the latter yielded 

 349 grains weight of seeds, whereas GO on the covered-up 

 plants yielded only 63 grains, and many of the seeds in the 

 latter lot were poor and aborted. Therefore the flowers 

 which were visited by bees produced between five and six 

 times as many seeds as those which were protected. The 

 covered-up plants not having been much exhausted by seed- 

 bearing, bore a second considerable crop of flower-stems, 

 whilst the exposed plants did not do so. 



Cytisus laburnum (Leguminosae). Seven flower-racemes ready to 

 expand were enclosed in a large bag made of net, and they 

 did not seem in the least injured by this treatment. Only 

 three of them produced any pods, each a single one ; and 

 these three pods contained one, four, and five seeds. So 

 that only a single pod from the seven racemes included a 

 fair complement of seeds. 



CupJiea purpurea (Lythracese). Produced no seeds. Other flowers 

 on the same plant artificially fertilised under the net yielded 



Vinca major (Apocynaceae). Is generally quite sterile, but some- 

 times sets seeds when artificially cross-fertilised : see my 

 notice, ' Gardeners' Chronicle,' 1861, p. 552. 



V. rosea. Behaves in the same manner as the last species: 

 'Gardeners' Chronicle,' 1861, pp. 699, 736, 831. 



Taberncemontana echinata (Apocynacese). Quite sterile. 



Petunia violacea (Solanacese). Quite sterile, as far as I have 

 observed. 



Solatium tuberosum (Solanaceae). Tinzmann says ('Gardeners' 

 Chronicle/ 1846, p. 183) that some varieties are quite sterile 

 unless fertilised by pollen from another variety. 



Primula scotica (Primulaceae). A non-dimorphic species, which 

 is fertile with its own pollen, but is extremely sterile if 

 insects are excluded. J. Scott, in ' Journal Linn. Soc. Bot.' 

 vol. viii. 1864, p. 119. 



Cortusa matthioli (Primulaceae). Protected plants completely 

 sterile; artificially self-fertilised flowers perfectly fertile. 

 J. Scott, ibid. p. 84. 



Cyclamen persicum (Primulaceae). During one season several 

 covered-up plants did not produce a single seed. 



Borago officinalis (Boraginacese). Protected plants produced 

 about half as many seeds as the unprotected. 



Salvia tenon (Labiatse). Quite sterile ; but two or three flowers 



