TRANS. ST. LOUIS ACAD. SCIENCE. 



the surprisingly interesting results of which are detailed by him 

 in the succeeding paper. 



GERMINATION. 



The seeds of Yucca germinate easily, the cotyledon remaining 

 partly in the ground * within the seed, extracting its liquified con- 

 tents, and never grows into a leaf-organ ; the first leaf issues from 

 a slit in the cotyledon opposite the remnants of the seed ; the suc- 

 ceding six or eight leaves of the first season following in § 

 order, which, in the further growth of the plant, gradually changes 

 to the higher orders of $ and further. From the nodes of the very 

 short axis, stout white rootlets break through the back of the 

 leaves, the first one through the back of the cotyledon, opposite 

 the first leaf, while the original radicle withers away. The Cali- 

 fornian T. Whipplei is the only one in which the axis, together 

 with the base of the leaves, swells up into a sort of bulb. 



In the second season, a stout, cylindrical secondary axis origi- 

 nates from the axil of one of the earliest of last year's leaves, 

 covered with scale-like leaf-rudiments, and eventually producing 

 from its nodes the rootlets which are to nourish the plant. This 

 secondary axis takes a horizontal direction in all the species I 

 could examine, especially in the different forms of T. jilamen- 

 tosa; only in T. angustifolia I have always found it to grow 

 straight downwards, continuing this direction through, at least, 

 the third and fourth year, and perhaps longer. Some observations 

 seem to indicate that T. gloriosa develops in a similar manner. 

 The terminal bud of this secondary axis does not seem to form 

 leaves as long as the primary leaf-bud continues to grow, and 

 probably not until it has produced a flowering stem, and perhaps 

 not even then for years. At last, however, the secondary axis 

 branches out, if horizontal, near the surface of the soil, if perpen- 

 dicular, as in T. angustifolia, at a certain depth, even two or three 

 feet, below it, forming horizontal branches, and eventually send- 

 ing out leafy shoots above the surface. Some species are sur- 

 rounded by such offshoots, thus forming clumps or thickets ; T. 

 baccata, T. gloriosa, T. jilamentosa, behave in this way, while 

 T. angustifolia is said to do this much more sparingly, and T. 

 aloi folia quite rarely. 



*The very similar seeds of Agave have a very different development; in their germi- 

 nation the cotyledon grows into a leaf, bearing the remnants of the seed on its tip- 



