392 



BOTANY OF THE LIVING PLANT 



reliable record. In the Devonian Period, long before there were any 

 Flowering Plants, there is abundant evidence of Fungal structure 

 existing under conditions favourable to that habit. It does not, 

 however, follow that all organisms which adopted a " fungal " habit 

 early were allied to one another, nor that all Fungi originated at 

 the same time. The existence of parasitic and saprophytic Seed- 

 Plants is a warning against such an assumption. We should rather 



Fig. 291. 



Harveyella mirabilis, growing as a colourless parasite on the thallus of Rhodomela, 

 one of the Red Algae. Longitudinal section of Rhodomela bearing the parasite, with 

 a mature cystocarp, the fertile filaments of which are black. The cells of the 

 host with food-material are dotted ; those which are exhausted are left blank. (After 

 Sturch.) 



be prepared to recognise that " Fungi " have originated along more 

 than one line of Descent, and probably at different times, from very 

 early periods omcards. It is natural to seek for some Algal origin 

 for them, for in many features they resemble Algae. At least two 

 general sources can be suggested, though the actual points of connec- 

 tion by descent may have been numerous. One is from non-septate 

 Algae, such as the Siphonales. This might have given rise to those 

 non-septate Fungi which are called Phycomycetes, from their 

 Alga-like features. The other is from septate Algae ; and the view 



