148 PLANT LIFE. 



or sporangium, and may be either motile, that is, zoospores, 

 as in the genera Saprolegnia and Cystopus ; or non-motile, 

 as in Mucor, and in the large group known as Ascomycetes, 

 where the sporangia contain a definite number of spores, 

 usually eight, and are called asci. 



(2) Sexual Mode. — The sexual fungi are those most 

 nearly allied to the algse, from which they are derived, in 

 fact in many instances the only observable difference between 

 certain algae and fungi turns on the complete absence of 

 chlorophyll in the latter ; hence, as would be expected, the 

 sexual modes of reproduction run parallel in the two 

 groups, and will be described in detail under the respective 

 orders. At present it will be sufficient to enumerate the 

 most prominent modifications of sexual reproduction, with 

 examples of each. (1) Zygospores resulting from the con- 

 jugation of two morphologically similar branches of the 

 mycelium, as in the species of Mucor, Rhizopus, etc. (2) 

 The formation of an oosphere which is fertilized by motile, 

 ciliated antherozoids, Monoblepharis. (3) The oogonium 

 contains one or several oospheres that are fertilized by 

 passive antheridia, consisting of the inflated tips of slender 

 branches formed on the same branches as the oogonia, or 

 on distinct branches. The antheridium comes in contact 

 with the wall of the oogonium, pierces its wall by means 

 of one or more fertilizing-tubes, through these tubes the 

 protoplasm passes from .the antheridia and mingles with 

 the oospheres. 



It is well known that certain species, belonging to widely 

 separated natural orders of Phanerogams, have degenerated 

 so far from the typical condition as to have lost the power 

 of forming chlorophyll, and consequently, like the fungi, 

 have become parasites or saprophytes : the species of 



