33» 



LECTURE XX. 



materials. Very frequently, at the end of the period of vegetation, nothing more 

 remains of the entire richly-leaved and rooted plant developed in summer, than simply 

 a reservoir of reserve-materials, in connection with one or more buds. This is the 

 case for example in species of Ophrys, in Aconitum napelltts, and in most plants with 

 bulbs and tubers (e.g. Colchicum : Fig. 227). The main mass of such a perennial 

 body consists of parenchymatous tissue filled with plastic reserve-materials ; while 

 the germinal shoots to be developed later persist through the winter in the form of 

 small buds. On the whole, the principle is the same in seeds also ; the parts of the 



embryo properly capable of development 

 (i. e. the plumule and radicle) which they 

 contain are extremely small, even in very 

 large seeds, while the mass of the reserve- 

 materials is incomparably larger. These 

 reserve-materials are either deposited in the 

 endosperm, from which the young plant 

 subsequently absorbs its nutritive matters 

 on germination ; or the first two leaves 

 of the seedling, the so-called cotyledons, 

 themselves grow to an enormous size, and 

 become filled with the reserve-materials, 

 which are then conveyed on germination 

 forthwith into the tissues of the growing 

 organs. For the elucidation of the matters 

 of organisation which, though closely con- 

 nected with nutrition, are only slightly 

 touched upon here, I must refer to the 

 figures and explanations distributed thuough- 

 out the text of this lecture. 



The form in which the plastic materials 

 are preserved in the reservoirs of reserve- 

 materials may be very various; the main 

 point always being that, in addition to 

 proteid substances, non-nitrogenous com- 

 pounds also are present, the mass of which 

 usually far preponderates. These latter, so 

 far as root-stocks, bulbs, tubers, and other 

 succulent reservoirs of reserve-materials are 

 concerned, are usually carbo-hydrates, with 

 a more or less considerable percentage of 

 fat. In seeds, on the other hand, it is more frequently the case that the starch 

 entirely disappears on ripening, and, together with the proteid matters, large 

 quantities of fat only remain over as reserve-materials. 



The form in which the proteid substances come to rest in the reservoirs of re- 

 serve-materials may be that of protoplasm itself, at any rate in succulent organs, such 

 as bulbs, tubers, and rhizomes ; at least in many such cases considerable quantities 

 of living protoplasm are found in the reservoirs of reserve-materials, which, when 



FlC'azS. — Bulbs of Fritillaria imperialis in November. , 

 A longitudinal section of the entire bulb (reduced) ; z z the 

 united lower portions of the bulb-scales, b b their free upper 

 portions— they surround a cavity / which contains the remains 

 of the decomposed flower-stalk. In the axil of the innermost 

 leaf of the bulb is the bud k which will develope in the follow- 

 ing year. Its first leaves will fbrm the new bulb, while its 

 stem'developes as the flowering-stalk — the root w springs from 

 the axis of this bud, B longitudinal section of the apical 

 region of the next year's bud; j apex of the stem, b b* bb" 

 youngest leaves. 



