402 



LECTURE XXVIII. 



where of course the formation of buds does not occur, we may probably recognise 

 chiefly a provision for protecting the substance of the growing-point, which is as 

 delicate as it is important. The same explanation applies to the similar depression 

 of the growing-point in the neighbouring tissue (in this case surrounding it on all 

 sides) on the likewise leafless shoots of species of Fucus, where a narrow long slit at 

 the end of each shoot opens into a narrow cavity, the base of which is occupied by 

 the growing-point, which here, as Rostafinski has shown, exhibits a series of curious 

 apical cells. A very similar arrangement also protects the growing-point of the sub- 

 terranean creeping shoot-axis of the Bracken fern {Pteris aquilind), because here, in 



consequence of the extremely sparse pro- 

 duction of leaves, together with other 

 circumstances, no leaf-bud exists to enve- 

 lope the growing-point, and therefore the 

 leaves cannot protect the growing-point in 

 the soil. 



In Phanerogams which persist by 

 means of subterranean tubers or bulbs, it 

 not rarely happens that at the end of a 

 short (or occasionally long) subterranean 

 lateral shoot, a body filled with reserve- 

 materials is formed ; and this contains the 

 bud with the growing-point at the bottom 

 of a central cavity. In these cases, how- 

 ever, peculiar displacements of the leaves 

 and of the parts of the axis which support 

 the growing-point usually take place at 

 the same time. The elucidation of these 

 processes, however, would carry us much 

 too far ; the chief points will be clear from 

 the consideration of Fig. 299. 



In the researches, as numerous as they 

 are brilliant, of Thilo Irmisch, who 

 has done so much good service for our 

 knowledge of the subterranean organs of 

 plants, is to be found abundant material 

 derived from the observation of cases be- 

 longing to this category\ Here, again, it is evidently a matter of obtaining the 



FIG. 298.— Prothallium of a Fern seen from below, f growing 

 point ; a antheridia ; iv roots (slightly magnified). 



^ It is the phenomena of growth here treated of which especially comprehend the subject 

 of the very copious morphological literature. A more detailed consideration of the phenomena 

 belonging here would lead to a morphological review of the natural system ; from the general 

 point of view which I have attempted to establish in the preceding lecture, however, these 

 phenomena belong also to physiology ; in fact, they form in a certain sense one of the foundations 

 of the physiology of growth. 



This being the case, it would scarcely be to the purpose to quote this or that treatise for proof; 

 however, it may be welcome to those readers who are unacquainted with botanical literature 

 and seek further instruction, to find quoted here a series of the most important works affecting this 



