464 



LECTURE XXVIII. 



FIG. 300. — Longitudinal section of a young flower 

 of Geum rivals (slightly magnified). 



Similar depressions are occasionally met with in leaf-shoots also : this is par- 

 ticularly clear, for example, in the winter buds of the common Pine, as shown in 

 Fig, 301. At the end of the shoot of the previous year is situated the still quite 



embryonic rudiment 2 of the next year's 

 shoot, with the growing-point v. This 

 embryonic shoot, however, is protected by 

 means of an annular wall for the purpose 

 of passing the winter. This wall arises 

 from the tissue of the shoot of the previous 

 year, and produces numerous bud-scales, 

 J, which completely envelope the embry- 

 onic shoot of the next year. These bud- 

 scales, moreover, as Goebel has shown, 

 are simply abortive foliage-leaves, which 

 may be transformed by means of vigorous 

 nutrition into the ordinary green acicular 

 foliage-leaves of the Pine. 



I may, in conclusion, refer briefly to the 

 formation of the Fig, as a particularly 

 remarkable case of the depression of a 

 growing-point, and of a further departure 

 from the typical state of affairs dependent thereupon. The Fig, which in popular 

 language passes for the fruit of the Fig-tree, is as a matter of fact a structure of quite 

 a different nature from the ordinary fruits of Angiosperms. It is a so-called pseudo- 

 fruit. The Fig is a hollow structure pro- 

 vided with fleshy walls, which abound with 

 sugar. These walls are constituted by a 

 hollowed-out shoot-axis, on the inside of 

 which hundreds of small flowers (subse- 

 quently fruits) are situated : these latter 

 constitute the hard granules found in the 

 pulpy mass of a ripe Fig. Fig. 302, which 

 represents the development of a Fig (/- 

 III), shows that it is originally an ordi- 

 nary shoot, the growing-point of which, 

 however, after giving rise to several leaves 

 /a, assumes the form of a flat disc. In 

 the centre of this disc is situated the proper 

 apex of the shoot, w'hich takes no part in 

 further growth however : on the contrary, 

 '''^•3°i- it is the margin of the disc which retains 



the embryonic character, and therefore 

 constitutes an annular growing-point. By means of the tissue formed by this 

 there now arises a hollow cylinder, /// a, at the upper margin of which the leaves 

 previously developed are situated, while further below arise new ones in addition, 

 closing the opening of the cavity of the Fig above. 



