146 D. H. SCOTT. 



tion to the hypoJermal vessels, for as regards these no con- 

 fusion is possible. 



I have not succeeded in every case in demonstrating the 

 presence of rudimentary laticiferous vessels in the embryo 

 of the ripe seed. The stage of development at which the 

 embryo enters upon its resting state in the dry seed is 

 known to be more or less accidental. There are probably 

 individual ripe seeds in which the cell-divisions in question 

 have not yet taken place, and only occur at the commence- 

 ment of germination. On the other hand, the rudimentary 

 fibro-vascular bundles can invariably be distinguished with 

 certainty. It follows that Faivre's assertions, according to 

 which the ripe embryo consists essentially of parenchyma, 

 in which neither tracheae nor laticiferous vessels are '^ de- 

 veloped," give a very inaccurate representation of the real 

 state of the case. On the other hand, Schmalhausen^s 

 results agree fully with my own. 



The latex-vessels in process of formation are much easier 

 to distinguish as soon as germination has once begun. In 

 seeds which had lain twenty-four hours in earth, but showed 

 no external signs of germination, I found the rudimentary 

 hypodermal vessels pretty clearly differentiated (fig. 4). 

 They appear as longitudinal rows of somewhat elongated 

 cells, which are as a rule about half as wide and double as 

 long as the parenchyma cells. It is still easy to see that 

 they have been formed by the division of cells belonging to 

 the third, and in some cases to the fourth layer from the 

 surface. The sister cells, which lie on the inside, remain 

 smaller than the other parenchyma cells, and have evidently 

 undergone further cross-divisions, which are passed over in 

 the cells of the laticiferous vessels. As regards the cell- 

 contents, the differentiation is now very conspicuous. Both 

 the epidermis and the parenchyma cells still contain a 

 quantity of aleurone grains. The latter are entirely absent 

 from the young laticiferous vessels. These have uniform 

 finely granular contents, with a darker spot, which may 

 possibly indicate the position of the nucleus. 



In germinating seeds with the root just beginning to 

 show itself, the hypodermal laticiferous vessels are a little 

 further developed. Their contents now begin to assume the 

 characteristic appearance of latex, and can be distinguished 

 at once by their colour from those of all the other cells. 

 The cross-walls, however, are still completely preserved. 



In seedlings with the root protruding three to four mm. from 

 the seminal envelopes, the laticiferous vessels can be clearly 

 recognised in almost every part. It is at about this time 



