PLANT HYBRIDIZATION BEFORE MENDEL 99 



possible to him that "such a minute body should emit a tube of such 

 length, through which its contents were passed into the ovary, as as- 

 serted." (p. 8.) 



Later on (p. 8) he alludes to the matter again : 



". . . it is utterly impossible that such a minute body should emit 

 such a pipe and its contents, that is, emit it of its own substance," and 

 adds that he apprehends the truth to be "that by contact with the juices 

 of the cognate plant it acquires that which enables it to gain bulk for 

 such an elongation." 



Herbert noticed the fact that in species crosses (e.g., Passiflora 

 coerulea X ony china) the ovaries may develop as the result of the 

 fertilization stimulus (in this case forming "two fine plump 

 fruits, two inches long"), the interior remaining empty as a 

 bladder, "the outer coat of the fruit only having been fertilized 

 in consequence of the weakness of the cross-bred pollen." {ih.^ 

 p. 9.) In other cases, he comments, one may find a perfect ovary, 

 and seeds grown to full size, although "containing a perishable 

 lymph, and no sound kernel." It appears to Herbert that the fer- 

 tilization-process is one which may consist of gradual degrees, 

 and that "it follows therefore that a continued operation of the 

 pollen must be necessary to produce all these requisites for the 

 formation of a good seed." {ih.^ p. 9.) He speaks of the "fertiliza- 

 tion" of the seed-coats and of the "albumen" as a process inde- 

 pendent of the fertilization of the ovules, since the result of such 

 fertilization may cause the seeds to grow, although without de- 

 veloping an embryo. He finally concludes (p. 10) : 



"if, therefore, as I apprehend, the pollen tubes cannot reach the ovules 

 without deriving substance from the cognate juices of the style through 

 which they descend, it becomes easy to understand how there may be 

 sufficient affinity between them to carry on the process to the degree 

 necessary for quickening the capsule, but not to carry it on to the point 

 requisite and with the excitement and irritability necessary for reaching 

 the ovules, etc." 



Again, he continues, where adaptation of the two types is per- 

 fect, a perfect offspring is produced ; where it is not perfect, an 

 inadequate or weak fertilization occurs, and, "it is further to be 

 observed that there is frequently an imperfect hybrid fertilization 

 which can give life, but not sustain it well." Among these he 

 mentions Hibiscus palustris X speciosus^ of which the seeds al- 

 ways sprouted, but of which only one was saved to the third 

 leaf, when it perished. He states that of Rhododendron ponti- 



