134 BROOKLYN BOTANIC GARDEN MEMOIRS 



growing point where abundant food is available, or even take two years 

 in regions less favorably located. The characteristically biniicleated 

 haustoria are of large size and are easily demonstrated. 



I have examined several stems three years old but do not find 

 that the mycelium spreads out through the entire cortex and into the 

 bast as described by Wornle. G. clavipes brings about less increase 

 in development of wood tissue than G. biseptatum, but this may be 

 due to the fact that the mycelium does not approach the cambium as 

 closely. This species may develop strictly foliicolous sori in which 

 case the mycelium is very limited in extent. The sorus is then not 

 deep seated. Haustoria can be found in epidermal cells. 



Gymnosporangium transformans 



I have previously reported'' that two leaf-inhabiting species of Gym- 

 nosporangium can be distinguished on Chamaecyparis. The account of 

 the cultures in support of this statement is being published in another 

 paper. For convenience I shall call one form G. transformans. Its 

 aecidial form is Roestelia transformans on Aronia. Gymnosporangium 

 fraternum is an appropriate name for the second leaf form which 

 infects Amelanchier. The aecidium is very similar to that of Roestelia 

 Botryapites; I am not prepared to prove that it is R. Botryapites. A 

 cytological examination of cedar leaves infected with G. transformans 

 and G. fraternum reveals further characteristics by which they may be 

 distinguished. 



If we section a leaf of Chamaecyparis infected with G. transformans, 

 we find that the mycelium is especially abundant in the large inter- 

 cellular spaces of the spongy mesophyll and the hyphae push in be- 

 tween the cells of the palisade on all sides. No hyphae are to be found 

 in the epidermis. If the section includes the short vein of the leaf we 

 see that hyphae are prevented in some way from entering the vascular 

 tissue. There is an irregular row of large cells surrounding the vein 

 of the leaf. These pericycle(?) cells do not normally form a per- 

 fectly closed ring; it is occasionally broken by smaller supporting 

 cells. In regions where the hyphae reach the large cells one can 

 find, here and there, that they have been penetrated by one or two 

 haustoria. Such infected cells are about one third larger than usual. 

 The cytoplasm is rather dense, including considerable stored food 

 and takes the gentian violet stain somewhat deeply. The nuclei 

 appear to be quite normal. Haustoria are also occasionally found in 

 mesophyll and palisade cells. The cells of the mycelium are bi- 

 nucleated and the nuclei stand out very clearly, especially where 



' Dodge, B. O. Report on further cultures of Gymnosporangia. Paper read 

 at the December meeting of the Botanical Society of America, New York, 1916. 



