THE IMPERMEABILITY OF SEEDS 57 



seeds, Handbuch der Samenkunde ; and he it was who pointed 

 out that even with plants where all the seeds seemed to be 

 permeable, there might be a small residuum of 2 or 3 per cent, 

 that continued to resist the penetration of water even after 

 some months' immersion (pp. 112, 113). But this botanist 

 made no special study of the subject, except in so far as it 

 was in relation to other seed-characters. 



It is to a recent Italian investigator, Dr Guiseppe Gola, Itsinvesti- 

 that we are indebted for an extensive series of studies of the Dr Gola. 

 nature and prevalence of this quality. His memoir, which 

 is entitled Ricerche sulla biologia e sulla fisiologia de Semi a 

 tegumento impermeabile, and which was published by the 

 Royal Academy of Sciences of Turin in 1905, will come as a 

 surprise to many who, like myself, were unaware that im- 

 permeable seeds are so frequently to be met with in the 

 plant-world. Although not able to follow him in all his 

 conclusions, I have found in his data the materials for a solid 

 foundation on which to begin in these pages a discussion of 

 the subject of impermeability. 



After ascertaining by a preliminary inquiry that this character 

 was exhibited most markedly by the seeds of Leguminosae 

 and then by those of Cistaceae and Malvaceae, Dr Gola 

 decided to limit his researches to those three families. His 

 method was well adapted to test the capacity of seeds in this 

 respect, since they were kept immersed in water for periods 

 of between thirty and eighty days. When swelling occurred, 

 it took place generally in from three to five days, and less 

 usually in about ten days. Impermeable seeds remained 

 unaffected at the end of the trials. The seeds of about 300 

 species of plants were exposed to this test, of which about 260 

 (belonging to 45 genera) were leguminous, whilst nearly 

 30 belonged to the Cistaceae, and 10 were malvaceous. 

 Temperate genera greatly predominate in his list of results, 

 not merely numerically, but also in the number of species 

 tested. Including the Acacias, we may here mention the genera 

 Astragalus, Cytisus, Genista, Lathyrus, Lotus, Medicago, Melilotus, 



