2o6 Morphology and Systematic Botany under [BOOK i. 



The views entertained on the subject of the development and 

 propagation of the lower Cryptogams down to the year 1850 

 were very uncertain and fluctuating. In some Algae, Fungi, 

 and Lichens certain organs of multiplication and propagation 

 were known, in others they were quite unknown ; some forms 

 appeared in places and under circumstances which seemed to 

 necessitate the assumption of spontaneous generation ; in 1827 

 Meyen declared that the small Algae, known as ' Priestley's 

 matter,' which are formed in stagnant water and even in closed 

 vessels, are produced by free generation, and Kiitzing endea- 

 voured to show this by experiment in 1833 ; some Fungi were 

 regarded as diseased growths from other organisms, many were 

 supposed to spring up spontaneously, though they might be 

 capable at the same time of propagating themselves by spores ; 

 this view was shared by even the best botanists with regard to 

 the most simple Fungi up to 1850. But the systematic inves- 

 tigation of the Algae and Fungi was as little hindered by 

 the notion of spontaneous generation after 1850 as that of 

 Phanerogams had been in the iyth century by the same 

 notion ; it was however at first affected by the view put forth 

 by Hornschuch in 1821 and by Kiitzing in 1833, that the 

 simplest of all Alga-cells (Protococcus and Palmella), once 

 produced spontaneously, could develop according to circum- 

 stances into a variety of Algae, and even of Lichens and 

 Mosses ; as some observers even now consider Penicillium 

 and Micrococcus to be the starting-points of very different 

 Fungi. There was a difficulty also in drawing the boundary- 

 line between the lower animals and plants ; the difficulty was 

 solved by classing all objects capable of independent move- 

 ment with animals ; thus whole families of Algae (the 

 Volvocineae, Bacillariaceae, and others) were claimed by the 

 zoologists, and when the swarmspores of a genuine Alga were 

 seen for the first time in the act of escaping, the phenomenon 

 was described as the changing of the plant into an animal. 

 Trentepohl in 1807, and Unger in 1830, explained in this way 



