The Sex and Generative Organs of Plants. 269 



form of a cone-like membrane around the cone-like ovule, and 

 towards its top, and at last only leave its point free and 

 open. At this period the delicate fecundating tube of the 

 pollen granule comes into contact with the ovules, reacHfhg 

 the embryo through the space left open by those thin cover- 

 ings. This takes place either by the pollen grains falling 

 of themselves on the stigma of the pistil, or by their being 

 conveyed thither by the wind, by insects, or by other causes, 

 by their fixing themselves on the stigma, and by lengthen- 

 ing their delicate fecundating tubes through between the 

 close packed cells of which it consists, down into the cavity 

 of the pistil ; or if it also is filled with cellular tissue, down 

 between its individual cells to the ovum. In this process, 

 the fecundating tubes often assume an extraordinary length 

 as compared with their thickness, and in spite of their ex- 

 ceedingly delicate organization, increase with immense rapi- 

 dity in length. 



The cellular tissue in the style and along their course 

 through the fruit downwards to the ova, is exceedingly 

 close, delicate, and moist, and appears to support and 

 nourish the fecundating tubes on their long journey, as 

 they lengthen themselves. The outer membrane or skin 

 of the pollen granule left behind on the stigma, becomes 

 more thin and empty. The fine fluid in the fecundat- 

 ing tubes, in which exceedingly small granules swim^ in 

 short the fovilla, shews itself in the liveliest motion during 

 the penetration of the tubes to the ova. When the pol- 

 len tube has once arrived at the ovum, it finds the al- 

 ready described embryo sac ready to come into direct con- 

 tact with it, and thus there probably results a transfusion 

 of the fovilla into the embryo sac. We recognise at least 

 after the pollen tube has entered into that cell, almost 

 constantly, a muddiness in it, which is caused by a thick- 

 ening of its contents i, e. by a cellular deposit. This feet has 

 been observed by many botanists and by myself, and there is 



