77 



dies. In Campanula Medium and in Cucurbita Pepo they are 

 also found; and M. Fritzsche starts the opinion that they 

 should be regarded as diseased pollen granules. In Scabiosa 

 pubescens he found two such intermediate bodies, which ap- 

 peared to be encased one in the other. (These intermediate bo- 

 dies of M. Fritzsche are cells and their contents, which occur 

 in the pollen vesicles of numerous plants, and have been over- 

 looked by him. When these cells in the interior of the vesi- 

 cles have large cellular nuclei, as in many Liliacece, such a 

 case as is related of Scabiosa pubescens becomes intelligible. 

 Rep.) The intermediate bodies, however, also occur in some 

 forms of pollen which have no apertures, as in Pinus and La- 

 riX) where the pollinic vesicle has two outer linings. The 

 drawing given of the pollen of Pinus sylvestris is one of the 

 most unsuccessful; in nature it has quite a different aspect. 



The subject of the second part of M. Fritzsche's memoir is 

 the form of the pollen. He first treats -of the pollen masses 

 and then of the pollen grains ; the former occur in the Or- 

 chidece, Asclepiadece, and in the genus Inga, which was pre- 

 viously known. The individual grains, of which the pollen 

 mass of the Orchidece consists, possess but one tunic, and there- 

 fore the inner one according to M. Fritzsche, yet the struc- 

 ture of this membrane but too plainly evinces that it is nearly 

 related to the outer ones of other kinds of pollen. In the 

 grains of the genus Asclepias he has not only observed two 

 tunics but even an exintine. 



Then follows a natural division of the pollen grains, ac- 

 cording to the number of tunics. 



1. Pollen grains with one tunic. To this section belong 

 Cauliniafragilis, Zanichellia pedunculata, Zoster a, and Najas 

 major. The confervoid pollen described in Zostera was dis- 

 covered, described, and figured many years ago by my friend 

 Nees von Esenbeck. 



2. Pollen grains with two tunics. Under this section are 

 classed almost all the forms of pollen, and we may properly 

 speaking regard those cases where fewer or more than two 

 membranes occur as exceptions. They divide themselves into 

 two groups, according to the presence or absence of the aper- 

 tures in the outer coat ; cohesions occur in both cases. 



A. Grains without apertures. The peculiar geniculated 



