DR. M. J. SCHLEIDEN ON PHYTOGENESIS. 28? 



tragacanth and many of those substances commonly aiTanged 

 under vegetable mucus. It is this gelatin which is ultimately 

 converted by new chemical changes into the actual cellular 

 membrane, or its thickening layers, and into vegetable fibre. 



I now return to the subject itself. There are two places in 

 plants AAhere the formation of new organization may be ob- 

 served most easily and clearly, from their being cavities closed 

 by a simple membrane, viz. in the large cell which subsequently 

 contains the albumen of the seed, the embryonal sac, and at 

 the end of the pollen tube, from which the embryo itself is 

 developed. They are chiefly distinguished from each other by 

 the embryonal sac, never originally containing starch, but pro- 

 bably, in general, the saccharine solution, (whence arises the 

 sweet taste of unripe pod fruits and cerealia,) or gum. 



The pollen on the contrary constantly contains starch, or the 

 above-mentioned granular mucus representing it, as an essential 

 constituent part. The so-called vegetable Spermatozoa will pro- 

 bably on more accurate examination be generally reduced to 

 one of these substances. These substances, however, are soon 

 dissolved, and change either into sugar or into gum ; both, at 

 times, even before the pollen grain has commenced sending forth 

 tubes on the stigma, frequently in the progress of the descent 

 of the tube through the style to the ovule ; so that in some cases 

 even unaltered starch is still found in the embryonal end. 



At both these places the above-mentioned minute mucous 

 granules very soon originate in the gum, upon which the solution 

 of gum, hitherto homogeneous, becomes opalescent, or, through 

 the presence of a larger mass of granules, even opake. Single, 

 larger, more sharply defined granules (fig. 2 above) now become 

 apparent in this mass; and very soon afterwards the cytoblasts 

 occur (fig. 2 below,) appearing as it Avere hke granular coagula- 

 tions around the granules. The cytoblasts, however, in this free 

 state grow very considerably ; and I have observed, for instance 

 in Fritillaria pyrenaica, a gradual expansion from 0'00084 to 

 O'OOl Prussian inch. 



As soon as the cytoblasts have attained their full size, a deli- 

 cate, transparent vesicle rises upon their surface : this is the 

 young cell, which at first represents a very flat segment of a 

 sphere, whose plane side is formed by the cytoblast, and the 

 convex side by the young cell, which is situated on it somewhat 

 like a watch glass on a watch. In its natural medium, it is di- 



