404 New combe. — On the Cause and Conditions 
Juglans nigra , L. 
J uncus effusus , L. 
Lamium garganicum, L. 
Melianthus major , L. 
Myrrhis odorata , Scop. 
Pterocarya fraxinifolia , N utt. 
Ricinus communis , L. 
Sambucus nigra , L. 
Silene viridiflora , L. 
Taraxacum Dens-leonis , Desf. 
Triticum repens , L. 
Ur tic a dioica , L. 
FzVz# Fab a, L. 
Mais, L. 
This work was begun in the Botanical Laboratory of the 
University of Leipzig under the direction of Professor Pfeffer, 
to whom the author feels himself greatly indebted, and was 
completed in the University of Michigan. 
1. Lysigenous Cavity-formation during Primary 
Growth. 
As far as observation has extended, all cavity-formation 
during primary growth is in its beginning schizogenous. But 
this splitting apart of cells before collapse of cells ensues may 
be on the one hand very extensive, while on the other hand 
it may go no farther than the formation of small intercellular 
spaces. The process has been described for several plants by 
Frank 1 , Trecul 2 , and others, and a general review of the matter 
is given by De Bary 3 . The cause for the appearance of these 
schizogenetic clefts is to be found in the rapid extension of the 
peripheral zones of tissue opposed to the more slowly extend- 
ing or wholly non-extending tissue in the localities where the 
clefts arise. 
Using for illustration only those plants which have been 
the subjects of my own observation, the leaves of Allium 
Cepa , the peduncle of Taraxacum Dens-leonis , the upper part 
of the stem of Vicia Faba , and the stem of Caltha palustris , 
may be cited as examples in which the splitting apart of cells 
during primary extension gives rise to central cavities of 
considerable size before any cells die. 
1 Frank, Beitr. zur Pflanzenphysiologie. Leipzig, 1868, p. 145. 
2 Trecul, Ann. Sci. Nat. 4® ser. I, p. 166. 
3 De Bary, Vergleichende Anatomic, §§ 51, 52. 
