344 



LECTURE XXI. 



seedling (embryo) is removed from the seed of the Indian corn (Maize), Barley or 

 other plant, and the endosperm alone laid in moist warm earth, its starch is not 

 dissolved and transformed into sugar. Still more evident than in such cases 

 appears the action of the growing seedling on the reservoir of reserve-materials, in 



the germination of the stone of the 

 Date ; for here the non-nitrogenous 

 reserve-material consists of hard 

 cellulose, which is deposited in the 

 endosperm in the form of thickened 

 |\ ' ( i§]^T\ 11 IT'' ^- I cell-walls, and which constitutes the 



great mass of the date-stone. The 

 embryo, at first very minute, pro- 

 trudes its root and plumule at the 

 beginning of germination (as seen in 

 Fig. 236), and only the uppermost 

 portion of the primary seed-leaf, 

 which now gradually develops into 

 a cup-shaped absorbing organ, be- 

 coming larger and larger, remains 

 within the endosperm. This organ, 

 consists of very delicate parenchyma, 

 and excretes ferments which dissolve 

 the hard endosperm in its immediate 

 neighbourhood. The products of 

 solution are absorbed by the organ, 

 and then conveyed into the growing 

 parts of the seedling ; until finally 

 the whole of the hard date-stone is 

 dissolved, and its cavity occupied by 

 the developed absorbing organ. The 

 seed of Phyfelephas (known under 

 the name of Vegetable Ivory), which 

 is at least a hundred times larger 

 than the date-stone, and the endo- 

 sperm of which consists of much 

 harder cellulose, behaves similarly. 



The action of those Fungi which 



destroy wood and kill trees may be 



compaied directly with the action of 



such seedlings on their endosperm ; 



the thin mycelial threads of these 



Fungi, as has been shown by Robert 



Hartig in his magnificent work, penetrate into the alburnum and heart-wood of 



trees, evidently because they excrete ferments at their growing apices, which dissolve 



the hard cell-walls of the wood. 



Attention was first drawn to the occurrence of peptonising ferments in the 



FIG. i-^f^.—C&xmmTi'CmaoiPlKenixdacfylifira. /transverse section 

 of the resting seed ; //, ///, /f stages in the germination (/Knat. size) ; 

 A transverse section of the seed IVsXxx; B transverse section of //•" at 

 xy ; C ditto at zz; e the horny endosperm ; s sheath of cotyledon ; s/ its 

 petiole ; ^ its apex, developed into an absorbing organ which gradually 

 exhausts the endosperm, and at length replaces it ; w the primary root ; 

 iv' lateral roots ; d'i" the leaves which succeed the cotyledon, 6" becomes 

 the first foliage leaf; in B and C its folded lamina is seen in transverse 



