Hill. — Studies in Seed Germination. 
216 
resembling that of some Monocotyledons, while In Echinocystis the cotyle- 
dons are epigeal and the germination of the seed is of the usual cucurbita- 
ceous type. 
Dunn, in his revision of the genus Mar ah, enumerates eleven species, 
and seeds of five of these have been received at Kew. 1 The general type 
of germination appears to be similar throughout the genus, though differences 
in detail may occur. 
The least specialized type of germination has been found to occur 
in M. fabaceus , and M. horridus , the species first examined at Kew, is 
the most highly developed, whilst M. macrocarpus, M. muricatus , and 
M. micranthus more nearly approach the condition shown by M. horridus. 
The plant figured by Asa Gray and Darwin under the name Megar- 
rhiza catifornica is probably a seedling of Mar ah macrocarpus, Greene, 
though the herbarium specimens referred to Megarrhiza catifornica , Torn 
and S. Wats., have been found to belong to Marah fabaceus , Greene. 
Asa Gray 2 was the first to observe and describe the peculiar germi- 
nation of the seeds of Megarrhiza catifornica, and subsequently Darwin 3 
made them the subject of careful study, and added several important 
details to the description given by Gray. Darwin’s account is detailed 
and exhaustive, and the only excuse for the present contribution lies in 
the fact that the germination of the seeds of other species has been studied 
and has rendered possible a comparative account of seed germination in 
the genus. 
Marah fabaceus, Greene. — In this species the two cotyledons are 
fused together towards the base and never leave the seed, and their 
petioles are united to form a short tube. On germination, the petiole tube 
elongates, and the plumule and radicle are carried out of the seed. The 
tube is only about 6 mm. long, but on emerging from the micropyle it 
bends downwards, and the radicle then breaks through the tip and pene- 
trates deeply into the soil, leaving the outer portions of the end of the 
petiole tube as a frayed edge, much in the same way as occurs with the 
hypocotyl of the Radish ( Raphanus ) (PI. V, Fig. 1). 
When the root has become well established by sending out lateral 
roots, the plumule breaks through the petiolar tube opposite the point 
of emergence of the root, and in time appears above the surface of the soil. 
At the same time a hypocotyledonary tuber begins to be formed by 
the re-storage of part of the reserve materials contained in the fleshy 
cotyledons (Fig. 2). This underground tuber increases in size as a result 
1 Seeds were kindly sent by Mr. H. F. Shorting, Huntington Beach, California, Professor 
H. M. Hall, College of Agriculture, Berkeley, California, Mr. W. W. Whitney, San Diego, Cali- 
fornia, Dr. J. N. Rose, Smithsonian Institution, Washington, and Mr. F. R. S. Balfour of Dawyck. 
2 Amer. Journ. Science, vol. xiv (1877), pp. 21-24, with Figs., and the Botanical Text Book, 
ed. 6, Pt. I, Structural Botany (1879), PP* 2 °> 2T > Figs. 43, 44. 
3 Darwin : Power of Movement in Plants, 1880, pp. 81-3, and Fig. 58 A. 
